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STEAM-BOILERS. 



BY 

CECIL H. PEABODY and EDWARD F. MILLER 

Professor of Marine Engineering Assistant Professor of Steam 

and Naval Architecture, Engineering, 

Massachusetts Institute of Technology. 



FIRST EDITION, 



FIRST THOUSAND. 




NEW YORK : 

JOHN WILEY & SONS, 
London: CHAPMAN & HALL, Limited. 

1897. 







Copyright, 1897 
C. H. PEABODY and E. F. MILLER 



/0 b 



0^ 



KORERT PRUMMONLV ELECTROTYPER AND PKINTER, NEW YORK 



PREFACE. 



In this book we have attempted to give a clear and con 
cise statement of facts concerning boilers, and of methods of 
designing, making, managing, and caring for boilers. Though 
the book is intended primarily for the use of students in 
technical schools and colleges, it is hoped that it may be 
found useful to engineers in general. 

There is given a description of various types of boilers in 
common use. Following this is a discussion of combustion, 
corrosion, and incrustation, with a statement of the most recent 
investigations and conclusions on these important subjects. 
We are fortunately able to give a satisfactory table of the 
compositions of American fuels — the first, so far as we are 
aware, that has been published. 

A statement is given of the proper and of the customary 
sizes and form of furnaces, and of the methods of firing. In 
the present unsatisfactory condition of the chimney problem 
we have contented ourselves with giving the ordinary theory 
and pointing out its defects, together with the common ways 
of proportioning chimneys. 

Tables of grate-areas and heating-surfaces, and of other 
proportions of furnaces and boilers, have been made up from 
the oest current practice for stationary, locomotive, and 
marine boilers. 

In the chapter on strength of boilers we have given briefly 
the methods and conditions for testing materials and for 
making boilers, and the properties which such materials 



IV PREFA CE. 

should have. Especial attention is given to the properties 
and proportions of riveted joints, deduced by Professors 
Lanza and Schwamb from tests at the Watertown Arsenal. 
Simpler calculations of stresses in the members of boilers are 
explained, and more complex ones, depending on the theory 
of elasticity and theories of beams and continuous girders, 
are illustrated by examples. 

A description is given of staying and other details affect- 
ing the design and construction of boilers, and of such acces- 
sories as safety-valves, gauges, and steam-traps. In order 
to give a conception of the methods and conditions of boiler- 
making, we have given a description of a modern bciler-shop 
and the machinery and processes used in it. 

In the chapter on boiler-testing we have given the 
methods used in the laboratories of the Massachusetts Insti- 
tute of Technology, including gas analysis, measurement of 
air used, and temperature, determinations in the furnace and 
chimney. 

Finally, the principles and methods set forth in tr e earlier 
chapters are brought together and illustrated by applying 
them to the design of a boiler of a common type. For our 
own students this chapter serves as an introduction to a 
course in machine design given by Professor Schwamb, who 
has kindly furnished us with methods and materials which he 
has collected and developed in connection with the design- 
ing of boilers. 

In the appendix are given various useful tables, such as 
logarithms, natural trigonometric functions, areas and circum- 
ferences of circles, proportions of rods and screws, and proper- 
ties of saturated steam C. H. P. and E. F. M. 

Boston, February i, 1897. 



CONTENTS. 



CHAPTER I. 

PAGZ 

Types of Boilers i 



CHAPTER II. 
Fuels and Combustion 37 

CHAPTER III. 
Corrosion and Incrustation 65 

CHAPTER IV. 
Settings, Furnaces, and Chimneys 91 

CHAPTER V. 
Power of Boilers 130 

CHAPTER VI. 
Staying and Other Details 148 

CHAPTER VII. 
Strength of Boilers 170 

CHAPTER VIII 

Boiler Accessories 235 

v 



VI CONTENTS. 

CHAPTER IX. 
Shop-practice 272 

CHAPTER X. 
Testing Boilers 300 

CHAPTER XI. 
Boiler Design 323 

APPENDIX 357 

INDEX 369 



STEAM-BOILERS 



CHAPTER I. 

TYPES OF BOILERS. 

Steam-eoilers may be classified according to their form 
and construction or according to their use. Thus we have 
horizontal and vertical boilers, internally and externally fired 
boilers, shell-boilers and sectional boilers, fire-tube and water- 
tube boilers: the several features mentioned may be combined 
in various ways so as to give rise to a large number of kinds 
and forms of boilers. Again, we have stationary, locomotive, 
and marine boilers, together with a variety of portable and 
semi-portable boilers. Locomotive boilers are always shell- 
boilers, internally fired, and with fire-tubes; and the re- 
strictions of the service have developed a form that has 
changed little from the beginning, except in the direction of 
increased size and power. Marine boilers present a much 
larger variety of form and construction, depending on the 
steam-pressure used and the size and service of the vessel to 
which they are supplied. The Scotch or drum boiler is more 
widely used than any other form at present, but the tendency 
to use high-pressure steam has led to the introduction of vari- 
ous forms of water-tube boilers for marine work. The variety 
of forms and methods of construction of stationary boilers is 
very wide: each country and section of a country is likely to 
have its own favorite type. Thus in New England, where 



2 STEAM-BOILERS. 

the water is good, cylindrical tubular boilers are largely used ; 
in some of the Western States, where water contains mineral 
impurities, flue-boilers are preferred; and in England, the 
Lancashire and Galloway boilers are favored; and again, 
various forms of sectional and water-tube boilers are now 
widely used. 

Cylindrical Tubular Boiler. — This type of boiler is shown 
by Fig. i and by Plate I. It consists essentially of a cylin- 
drical shell closed at the ends by two flat tube-plates, and of 
numerous fire- tubes, commonly having a diameter of three or 
four inches. About two thirds of the volume of the boiler is 
filled with water, the other third being reserved for steam. 
The water-line is six or eight inches above the top row of 
tubes. The tube-plates below the water-line are sufficiently 
stayed by the tubes ; above the water-line the flat plates are 
stayed by through rods or stays as in Plate I, by diagonal 
stays like those shown by Fig. 52, page 154, or otherwise. A 
pair of cylindrical boilers in brick setting are shown by Figs. 
36 and 37, on pages 92 and 93, with the furnaces under 
the front (right-hand) end. The products of combustion pass 
back over a bridge-zvall, limiting the furnace, to the back eud, 
then forward through the tubes and up the uptake to the flue 
which leads to the chimney. 

The shell commonly extends beyond the front tube-plate, 
as shown at the right in Fig. 1, and is cut away to facilitate 
the arrangement of the uptake. The boiler is usually sup- 
ported by cast-iron brackets riveted to the shell ; the front 
brackets may rest on or be fixed to the supporting side walls, 
but the rear brackets should be given some freedom to avoid 
unduly straining the boiler by expansion. Thus the rear 
brackets may rest on rollers, which in turn bear on a horizontal 
iron plate. The expansion takes place toward the back end of 
the boiler, and to allow for this expansion a space is left 
between the back tube-sheet, and the arch of fire-brick back 
of the boiler. 



TYPES OF BOILERS. 




4 S TEA M-B OIL EKS. 

The boilers shown by Fig. i and by Plate I each have 
two steam-nozzles, one near each end. The safety-valve is 
usually attached to the front nozzle, which is above the fur- 
nace. The steam-pipe leading steam from the boiler is at- 
tached to the rear nozzle, which is over the back end of the 
boiler, where ebullition is less violent, and consequently there 
is less danger that water will be thrown into the steam-pipe. 

Boilers of this type commonly have a manhole on top near 
the middle, and a hand-hole near the bottom of each tube- 
sheet, as shown on Plate I, to give access to the interior of 
the boiler and to facilitate washing out. Many boilers are 
now made with a manhole near the bottom of the front tube- 
sheet, in addition to the one on top. All parts of the boiler 
can then be cleaned and inspected whenever desirable. Some 
of the lower tubes must be left out when there is a manhole 
in the tube-sheet, but this is of small consequence, as the 
lower tubes are not efficient, and enough heating-surface can 
be provided elsewhere. The omission of the lower tubes re- 
quires also special stays for the portion of the tube-sheet left 
unsupported. 

The feed-pipe for the boiler shown by Plate I enters the 
front head at the left, below the water-line, and runs toward 
the back end of the boiler, where it may end in a perforated 
pipe leading across the boiler. The feed-pipe may enter the 
top of the boiler, near the back end, and terminate in a similar 
perforated transverse pipe below the water-line. 

A blow-off pipe leads from the bottom of the shell near the 
back tube-sheet. On the blow-off pipe there is a plug or valve 
which may be opened when steam is up, to blow out mud and 
soft scale that may collect in the boiler. The boiler is com- 
monly set with a slight inclination toward the rear so that 
mud may collect near the blow-off pipe. The boiler may be 
emptied by allowing the water to run out at the blow-off pipe. 

About half of the shell, two thirds of the back tube-sheet, 
and all the inside surface of the tubes come in contact with 



TYPES OF BOILERS. 



the products of combustion and form the heating-surface ; all 
the heating-surface is below the water-line. 

The boiler-setting, shown by Figs. 36 and 37 on pages 
92 and 93, is made of brick laid in cement or mortar; all 
parts that are directly exposed to the fire are lined with fire- 
brick. The walls have confined air-spaces to reduce transmis- 
sion of heat. The boiler front is commonly made of cast iron. 
and has fire-doors leading to the furnace, and ash-pit doors 
opening from the ash-pit, or space below the grate ; there are 
also large doors giving access to the tubes through the 
smoke-box at the front end of the boiler. The furnace is 
formed by the side walls, the bridge, and the lower part of the 
boiler front, which latter is lined with fire-brick above the 
grate. Doors through the rear wall give access to the space 
back of the bridge. The top of the boiler is covered by a 
brick arch or by non-conducting material. 

Two-flue Boiler. — The cylindrical flue-boiler differs from 
the tubular boiler mainly in replacing the fire-tubes by one 



or more large flues. 



Fig. 2 shows such a boiler with two 




Fig. 2. 



flues. This type of boiler is usually longer than a tubular 
boiler, but even so it has less heating-surface and is less 
efficient in the use of coal. Nevertheless the greater sim- 
plicity and accessibility for cleaning recommend* it where feed- 
water is bad. 

The setting of a flue-boiler resembles that for the cylin- 



S TEA M-BOIL EKS. 



drical tubular-boiler. 




The figure shows two loops at the top 
of the shell for hanging the 
boiler; a crude method of sup- 
porting, suitable only for small 
and short boilers. 

Plain Cylindrical Boiler. — 
In places where fuel is very 
cheap, especially where it is a 
waste product, as at sawmills, 
the plain cylindrical boiler is fre- 
quently used. Its external ap- 
pearance is similar to that of the 
two-flue boiler (Fig. 2), except 
that there are no flues and the 
ends are commonly hemispheri- 
cal or else curved to a radius 
equal to the diameter of the 
shell. Such plain cylindrical 
boilers are also employed to util- 
ize the waste gases from blast- 
furnaces. They are commonly 
30 to 42 inches in diameter and 
from 20 to 40 feet long. They 
have been made 70 feet long. 
With such extreme lengths spe- 
cial care must be taken to insure 
equal distribution of the weight 
to the supports and to provide 
for expansion. 

Lancashire Boiler. — This 
boiler, shown by Fig. 3, is a two- 
flue shell-boiler with furnaces 
in the tubes; it is therefore an 
internally-fired boiler, in which 
it differs from the two pre- 



TYPES OF BOILERS. 7 

ceding types, which arc externally-fired. The chief difficulty 
in the design of these boilers is to provide sufficiently large 
furnaces without making the external shell too large. As com- 
pared with the cylindrical tubular boiler, this boiler will be 
sure to have long, narrow grates, with a shallow ash-pit and a 
low furnace-crown: the boiler also appears to be deficient in 
heating-surface. In compensation, radiation and loss of heat 
from the furnace are almost entirely done away with, and the 
thick outside shell, with its riveted joints, is not exposed to 
the fire, as with the tubular boiler. The flues are made in 
short sections riveted together at the ends, thus forming a 
series of stiffening rings that add very much to the strength 
of the flues against collapsing. Conical through-tubes, ver- 
tical or inclined, give increased heating-surface, break up the 
currents of the hot gases, improve the circulation of the water, 
and strengthen the flues. These tubes are small enough at 
the lower end to pass through the hole cut in the flue for the 
upper end, and thus are readily put in or taken out for repairs. 

The flat plates at the ends of the shell are stayed by 
gusset-stays or triangular flat plates to the shell of the boiler. 
The boiler is provided with a manhole near the back end and 
a safety-valve near the front end. Steam is taken through a 
horizontal dry-pipe, perforated on the top. 

Galloway Boiler.— This boiler has two furnace-flues at the 
front end, like the Lancashire boiler. Beyond the furnace 
the two flues merge into one broad flue, having the upper and 
lower surfaces stayed by numerous conical through-tubes, like 
those shown in Fig. 3 for the Lancashire boiler. 

Cornish Boiler. — This boiler was developed in conjunction 
with the Cornish engine, and both boiler and engine long had 
a reputation for high efficiency. It differed from the Lanca- 
shire boiler in that it had but one flue; it formerly did not 
have cross-tubes. The one furnace of the Cornish boiler, with 
a given diameter of shell, can have better proportions than 
the two furnaces of the Lancashire boiler, but there is even 



o S TEA M-BOILERS. 

greater difficulty to get sufficient grate-area and heating-sur- 
face. The high economy shown by these boilers when used 
with the Cornish pumping-engine was due to a slow rate of 
combustion, and to the skill and care of the attendant, who 
was usually both engineer and fireman, and who was stimu- 
lated by a system of competition and awards, maintained by 
the mine-owners in that district. 

The Lancashire and the Cornish boilers are set in brickwork 
which forms flues leading around the outside shell, thus mak- 
ing the shell act as heating-surface. Fig. 4 gives a cross-sec- 




Fig. 4. 



tion of the Lancashire boiler and its setting. After the gases 
from the fires leave the internal flues they are directed into 
the flue a and come forward ; then they are transferred to the 
flue b and pass backward ; finally they come forward in the 
flue c, and are then allowed to pass to the chimney. This 
forms what is known as a wheel-draught. In some cases the 
gases divide at the rear and come forward through both side 



TYPES OF BOILERS y 

flues a and b, and uniting pass back through c and thence to 
the chimney, forming a split-draught. 

Vertical Boilers.— Boilers of this type rave a cylindrical 
shell with a fire-box in the lower end, and with fire-tubes run- 
ning from the furnace to the top of the boiler. Large verti- 
cal boilers have a masonry foundation and a brick ash-pit; 
small vertical boilers have a cast-iron ash-pit that serves as 
foundation. Vertical boilers require little floor-space; if 
properly designed they give good economy, or they may be 
made light and powerful for their size, when economy is not 
important. 

Fig. 5 shows a large vertical boiler designed by Air. 
Manning. It is made 20 to 30 feet high, so that there is a 
large heating-surface in the tubes. The shell is enlarged at 
the fire-box to provide a larger furnace and more area on the 
grate. The internal shell which forms the fire-box is joined 
to the external shell by a welded iron ring called the founda- 
tion-ring. This internal shell should be made of moderate 
thickness to avoid burning or wasting away under the action 
of the fire. Being under external pressure, the shell of the 
fire-box must be stayed to avoid collapsing. For this pur- 
pose it is tied to the outside shell at intervals of four or five 
inches each wry, by bolts that are screwed through both 
shells and riveted over cold, on both ends. The stays near 
the bottom have each a hole drilled from the outside nearly 
through to the inside end. Should any stay break or become 
cracked, steam will escape and give warning to the fireman. 

The tubes are arranged in concentric circles, leaving a 
space about ten inches in diameter at the middle of the 
crown-sheet; the corresponding space in the upper tube- 
sheet provides for the attachment of the nozzle for the steam 
outlet. 

There are numerous hand-holes in the shell outside of the 
fire-box, some near the crown-sheet, and some near the foun- 
dation-ring, and these are the only provision for cleaning the 



IO 



S TEA M-BOILEKS. 



WATER LEVEL 



wywjsM4s& 




wBsm 



Fig. 5. 



TYPES OF BOILERS. 



II 



boiler, which consequently is adapted for the use of good 
feed-water only. The feed-pipe enters the shell at one side 
and extends across the boiler; it is perforated to distribute 
the feed-water. 

The sides of the fire-box, the remaining surface of the 
tube-sheet allowing for the holes for the tubes, and the inside 




Fig. 6. 



of the tubes up to the water-line form the heating-surface: 
the inside of the tubes above the water-line form the super- 



12 



S TEA M-B OILERS. 



heating-surface, since it transmits heat from the gases to the 
steam and superheats it. 

This type of boiler has found favor at factories where 
floor-space is valuable, since a powerful battery of boilers may 
be placed in a small fire-room. 

A small vertical boiler adapted for hoisting, pile-driving, 
and other light work is shown by Fig. 6. It commonly has 
a short smoke-pipe, into which the exhaust steam from the 
engine is turned to form a forced draught and give rapid 
combustion. Under this treatment the upper ends of the 
tubes frequently g;ve trouble by leaking. To avoid this diffi- 
culty the tubes are sometimes ended in a sunken or submerged 
tube-sheet which is kept below the water-line, as shown by 
Fig. 7. The space between the edge of the tube-sheet 




Fig. 7. 

and the outside shell is likely to be contracted, and not to 
give proper exit for the steam formed on the tubes and 
crown-sheet. Furthermore, the cone forming the smoke- 
chamber above the tube-sheet is subjected to external pres- 
sure and is likely to be weak. 

A form of vertical boiler having a sunken tube-plate is 
shown by Fig. 8. It was at one time much used for steam 
fire-engines, but to save weight it was so crowded with tubes 



TYPES OF BOILERS. 



! 3 



and the water-spaces were so contracted that it gave mucl 
trouble when forced, as at a fire. 

Fire-engine Boiler. — A boiler for a steam fire-engine 
should be light and compact, able to make steam quickly and 




Fig. S. 



to steam freely when urged. They have small water-space 
and large heating-surface for their size, but are not economi- 
cal in the use of fuel. It is customary to use cannel-coal for 
fire-engines, as it burns freely without clogging. A forced 



14 STEAM-BOILERS. 

draught is obtained by exhausting steam up the smoke-pipe. 
When standing in the engine-house ready for duty the 
boilers are kept hot by connecting them to a heating- 
boiler in the basement. The connection is so made with 
snap-valves that it is broken by pulling the fire-engine out of 
position. 

Figs. 9 and 10 show a vertical section and two half-hori- 
zontal sections of the Clapp fire-engine boiler. The boiler has 
a cylindrical shell and a deep internal fire-box. From the 
crown-sheet a number of fire-tubes lead through the water 
and steam space to the upper tube-sheet. In the upper part 
of the fire-box there are a number of water-tubes that start 
from the side of the fire-box, make several helical coils, and 
then open into the water-space above the crown-sheet. 

There are three concentric sets of these helical coils, 
leaving a cylindrical space in the centre, which is occupied by 
a series of castings, shown in perspective and partly in section 
by Fig. 1 1. The casting is formed of an annular torus with a 
cross-tube, and an inverted U tube above. Water enters at 
the middle of the cross-tube, passes into the torus, and then 
up and out at the top of the U. 

The left half of Fig. 10 shows the helical tubes from above ; 
the right half shows the arrangement of the fire-tubes and 
the openings of the water-tubes. 

Marine Boilers. — A single-ended three-furnace Scotch 
marine boiler is shown in perspective by Fig. 12; Fig. 13 
gives the working drawings of a similar boiler with two fur- 
naces. The arrangement of the furnaces in the flues, is simi- 
lar to that for the Lancashire boiler, shown, by Fig. 3. The 
furnace-flue leads into a combustion-chamber, from which 
the products of combustion pass through fire-tubes to the 
uptake, which is bolted onto the front end of the boiler. 

The flues are from three and a half to four and a half 
feet in diameter; the size of the boiler depends on the 
number and size of the flues. Large boilers have as many 



TYPES OF BOILERS. 



15 




Fig 9. 



Fig. 11 



i6 



S TEA M-B OILERS. 



as four flues. A three-furnace boiler commonly has three 
combustion-chambers, while a four-furnace boiler may have 
two, into each one of which two furnaces lead. Double- 
ended boilers have furnaces at each end, and resemble 
two single-ended boilers placed back to back. A double- 
ended boiler is lighter, cheaper, and occupies less space than 



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8 SSSSS oo8S!SS »o 

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Fig. 12. 



two single-ended boilers. In the best practice there are 
two distinct sets of combustion-chambers for the two sets 
of furnaces. To still further lighten double-ended boilers, 
common combustion-chambers for corresponding furnaces at 
the two ends have been used. The results from such 
boilers have not been satisfactory, more especially when 



TYPES OF BOILERS. 



17 



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1 8 S TEA M-B OILERS. 

used under forced draught in the closed stoke-holes of war- 
ships; there has been so much trouble from leaky tubes 
under such conditions that forced draught has been aban- 
doned in many cases, and ships have consequently failed to 
make the speed anticipated. 

The circulation of water is defective in all Scotch boilers, 
and more especially in double-ended boilers. Considerable 
time — three or four hours — is always allowed for raising steam. 
Frequently some arrangement is made for drawing cold water 
from the bottom of the boiler and returning it near the water- 
line, while steam is raised. Haste and lack of care are liable 
to cause leakage from unequal expansion. The flue has the 
highest temperature of any part of the boiler and consequently 
expands the most, so that some allowance for expansion must 
be made or it will strain the tube-sheets and cause leaks. The 
methods of providing for expansion and at the same time 
stiffening the flues against collapsing under external pressure 
are shown on pages 210 to 216, and will be described in de- 
tail later on. 

Gunboat Boilers. — Some gunboats and other small naval 
vessels have not room under the deck for Scotch boilers. The 
form shown by Fig. 14 has been used on such vessels; it has 
two furnace-flues, leading to a common combustion-chamber, 
from which fire-tubes lead to the back end of the boiler. 

Locomotive-boilers. — The typical American locomotive- 
boiler is shown by Plate II. Fig. 15 gives a perspective view 
of a boiler of the locomotive type used for small factories, or 
where steam is required temporarily ; it has no permanent 
foundation, but is supported on brackets at the fire-box and 
by a pedestal-bearing on rollers near the back end. 

The locomotive-boiler consists essentially of a rectangular 
fire-box and a cylindrical barrel through which numerous tubes 
pass from the fire-box to the smoke-box, which forms a con- 
tinuation of the barrel, and from which the products of com- 
bustion pass up the smoke-stack. 



TYPES OF BOILERS. 



*9 



The fire-box is joined to the outer shell at the bottom by 
a forged rectangular foundation-ring, similar (except in shape) 




Fig. 15. 

to the foundation-ring of a vertical boiler. Near this ring are 
several hand-holes for clearing out the space between the fire- 
box and the shell, commonly called the water-leg. The boiler 



20 S TEA M-B OILERS. 

also "has a manhole at the top of the barrel. The water-leg is 
stayed by screwed stay-bolts riveted cold at the ends. 

The flat crown-sheet is stayed to a system of crozun-bars 
which rest on the side sheets of the fire-box and are also slung 
from the shell. Plate III shows a locomotive-boiler with a 
flattened top over the fire-box, to which the crown-sheet is 
stayed by through-bolts. Other methods and details of stay- 
ing crown-sheets will be given later. 

The tubes for a locomotive-boiler are smaller than for sta- 
tionary boilers (about two inches in diameter) and are spaced 
much more closely. This is to obtain a large heating-surface 
required by the high rate of combustion, which often exceeds 
one hundred pounds of coal per square foot of grate-surface 
per hour. The boiler works under a strong forced draught, 
produced by throwing the exhaust up the smoke-stack. 

The boiler is fastened rigidly to the frame of the locomo- 
tive at the smoke-box end ; a small longitudinal motion on the 
frame at the fire-box end is provided by expansion-pads, shown 
by Fig. 4, Plate II. 

Locomotive Type of Boiler — Reference has already been 
made in connection with Fig. 15 to a boiler of locomotive 
type used for stationary purposes. Plate IV shows a modi- 
fication of the locomotive type designed by Mr. E. D. Leavitt 
to give high evaporative efficiency. The boiler represented 
lias a barrel 90 inches in diameter, and it is 34 feet 4 inches 
long over all, It supplies steam at 185 pounds pressure to 
the square inch to the high-duty pumping-engine at Chestnut 
Hill Reservoir, Boston. 

The fire-box of this boiler is spread at the bottom to give 
increased grate-area, and contains two separate furnaces, shown 
by the section AA on Plate IV. The products of combus- 
tion pass through openings, shown by section BB, into a com- 
bustion-chamber, which has the section shown at CC. From 
the combustion-chamber, the gases pass through tubes to the 
smoke-box and uptake. As far as the combustion-chamber 



TYPES OF BOILERS. 21 

the top of the boiler is flattened to facilitate the staying of the 
crown-sheets of the furnace, passages, and combustion-cham- 
ber; the barrel of the boiler beyond the combustion-chamber 
is cylindrical. 

The boiler is somewhat complicated in construction and 
staying, and must be handled with care, especially in starting, 
to avoid straining from unequal expansion. It is adapted for 
the use of good feed-water only. 

Boilers of the locomotive type were at one time used for 
torpedo-boats. The fire-box was made shallower than for 
locomotive-boilers, and forced draught in a closed stoke-hole 
was used, the rate of combustion being even higher than on 
locomotives. Whatever may have been the reasons, it was a 
fact that this type of boiler, which is very reliable on locomo- 
tives, gave much trouble in torpedo-boats. 

Water-Tube Boilers. — The boilers thus far considered 
have an external shell containing a large body of water. Heat 
is communicated to the water through the shells or through 
the sides of internal furnaces, and also by carrying the gases 
through tubes or flues. The boilers and water contained, are 
heavy and cumbersome, and the shells under high pressure 
must be made very thick. If the boiler fails either through 
some defect or through carelessness of attendants, a disastrous 
explosion is likely to take place. If properly designed and 
made and if cared for by competent and careful attendants 
they are safe, reliable, and durable. The large mass of hot 
water tends to keep a steady pressure, though at the expense 
of rapidity of raising steam or of meeting a sudden demand 
for more steam. 

A large number of water-tube boilers of all sorts of shapes 
and methods of construction has been devised to overcome 
the admitted defects of shell-boilers. They all have the 
larger part of their heating-surface made up of tubes of moder- 
ate size filled with water. They all have some form of separa- 
tors, drum, or reservoir in which the steam is separated from 



22 S TEA M-B OILERS. 

the water; some of these boilers have a shell of consider- 
able size, thus securing a store of hot water and a good free- 
water surface for disengagement of steam. Such shell, drum, 
or reservoir is either kept away from the fire or is reached 
only by gases that have already passed over the surface of 
water-tubes. 

The tubes are of moderate or small diameter, and so can 
be abundantly strong even when made of thin metal. Even 
if a tube fails through defect in manufacture or through wast- 
ing during service, it will not cause a true explosion ; and yet 
the failure of a tube in a confined boiler or fire-room has fre- 
quently caused death b\ scalding. 

Water-tube boilers may be made light, powerful, and 
compact, and are well adapted for use with forced draught. 
Steam may be raised rapidly from cold water, but pressure 
falls as rapidly if the fire loses intensity, and fluctuations in 
pressure are likely to occur. The two greatest difficulties are 
to secure a proper circulation of water through the tubes 
and to properly separate the steam from the water. There 
are many joints that may give trouble by leaking, and some 
types have numerous hand-holes for cleaning the tubes, which 
may further increase the chances of petty leaks. 

A few water-tube boilers will be described as illustrations ; 
many others equally good will be passed by, since it will be 
impossible to describe all. 

Babcock and Wilcox Boiler. — This boiler, which is 
shown by Figs. 16 and 17, is a water-tube boiler having a 
cylindrical shell to furnish steam-space, and in which is the 
free-water surface for the disengagement of steam. The 
tubes are expanded into vertical headers at each end ; the 
front-end headers open into a cross-connection in communica- 
tion with the cylindrical shell, while the back-end headers are 
connected with a similar cross-connection by slightly inclined 
pipes. The tubes in each section are staggered so that the 
tubes taken as a whole are in horizontal rows, but not in ver- 



TYPES OF BOILERS. 



23 



tical rows— an arrangement that gives a better spreading of 
the products of combustion among the tubes. At each end 
of each tube are hand-holes that give access to the inside of 



6 




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the tube when it needs cleaning or scaling. By the aid of a 
brick bridge-wall at the end of the furnace and a continuation 
of this wall formed of special tiles through the tubes, tog-ther 



24 



STEAM-BOILERS. 




TYPES OF BOILERS. 2$ 

with a hanging bridge-wall similarly continued through the 
tubes, the products of combustion pass over the tubes three 
times on the way to the uptake at the back end of the boiler. 
The lower half of the cylindrical shell serves as heating-sur- 
face, but it is at such a height above the fire and is so 
shielded by the water-tubes that it is not liable to be over- 
heated. The boiler is hung from cross-girders front and back, 
which in turn are supported on iron columns, and the brick 
setting is only a screen to retain the heat. 

The circulation of the water in the boiler is down from the 
shell at the rear to the water-tubes, forward and upward 
through the tubes, in which course it is partially vaporized 
and consequently has a less average density, then up into the 
shell, at the front where the steam and water separate ; the 
water in the shell flows continually from the front to the rear 
to supply the current through the tubes. 

The Heine Boiler, shown by Fig. 42, page 106, resembles 
the Babcock and Wilcox boiler in general arrangement, but 
differs in that the tubes are expanded into one large header 
at each end^made of plate, properly stayed and provided 
with hand-holes. Again, the gases from the fire are con- 
strained to pass along the tubes instead of across them, for 
which purpose there are floors or nearly horizontal bridges of 
tiles, laid on two or three layers of tubes, instead of the nearly 
vertical bridges of tiles used in the Babcock and Wilcox boiler. 

The Root Boiler. — The general appearance of the Root 
boiler is shown by Fig. 18, and details of construction are 
shown by Fig. 19. Pairs of tubes are first expanded into 
headers at the end, as shown by 1, Fig. 19; then several 
pairs are assembled, as shown by 2, to form a vertical section, 
by the aid of bends, of which 3 gives further details. The 
joints between the bends and headers are made tight by aid 
of a metallic packing-ring shown by 4. The conical bearing 
on the bend shown by 5 expands the ring into a recess in the 
header, shown by 6, thus making a steam-tight joint. Each 



26 



STEAM-BOILERS. 




Fig. i 8. 




Fig. ig. 



TYPES OF BOILERS. 2J 

section has a steam-drum at the top, as shown in Fig. 18, 
and at the back end of the steam-drum are pipes leading up 
into the transverse steam-drum, and downward into a trans- 
verse water-pipe at mid-height of the boiler. Near each end 
of the mid-height water-pipe are vertical pipes communicating 
with the ends of a transverse mud drum, from which a scries 
of pipes lead to the sections of the boiler. The water circu- 
lation is down from the back ends to the mud-drums, then 
forward through the tubes to the front ends of the steam- 
drums, in which the steam and water separate, the steam 
passing into the transverse steam-drum, and the water re- 
turning through the back connections to the sections. The 
products of combustion pass over the tubes three times 
before escaping to the chimney. 

The Stirling Boiler. — This boiler, shown by Fig. 20, has 
three cylindrical drums at the top and a larger drum at the 
bottom, connected by tubes having a slight curvature at the 
ends. The two forward drums at the top have also a connec- 
tion below the water-line through pipes not indicated. All 
three upper drums have their steam-spaces connected by 
piping. The water-line is indicated by a dotted line. 

The feed-water is introduced into the rear upper drum, 
from which it passes down through the rear system of pipes, 
which act mainly as a feed-water heater, and enter the lower 
drum, where the water deposits any lime compound that it 
may contain, from whence it may be blown out at intervals. 
Fire-brick bridges cause the products of combustion to pass 
in succession through the three systems of water-tubes as 
shown by the arrows. 

The Cahall Boiler is a vertical water-tube boiler, shown 
by Fig. 21. It has an annular drum at the top and a cylin- 
drical drum at the bottom, connected by tubes and also by 
two large circulating pipes outside of the brick setting, one 
of which is drawn in the figure. The fire is in a brick 
furnace at one side of the boiler, from which the products of 



28 



STEAM-BOILERS. 



combustion pass back and forth across the tubes to and from 
the central space between the tubes. For this purpose there 
are two iron baffle-plates in the central space, as indicated in 
the figure. 

The water-line is carried ac about one third the height of 
the upper drum, and steam is drawn from a nozzle at the top. 




Fig. 20. 

The circulation is down the large exterior pipes to the lower 
drum, and then up the water-tubes to the upper drum. Man- 
holes give access to both drums, and in addition there are 
eight hand-holes in the top of the upper drum, so that any 
tube may be cut out and replaced without disturbing the 
others. 



TYPES OF B01LKKS. 



2 9 




Sir 




1 

I P 

til ! 




30 STEAM-BOILERS. 

Water-tube Marine Boilers. — With the advent of very 
high steam-pressures on steamships there has been a tendency 
to replace the Scotch boiler by some form of water-tube 
boiler. A large number of French merchant steamers and a 
few French naval vessels have been fitted with Belleville 
boilers, a type of water-tube boilers that had already found 
favor for stationary purposes. This type of boiler has also 
been used to some extent on the Great Lakes. Recently this 
boiler has been largely introduced in the English Navy. 
Other water-tube boilers, either designed specially for marine 
boilers or modified from land boilers, have been used to 
some extent. In the United States Navy some vessels have 
been fitted with both shell-boilers and water-tube boilers ; the 
former are intended for use in ordinary service, and the latter 
when running at high speed. 

The objects that are sought in water-tube boilers for 
steamships are a larger power for the weight and the ability 
to carry high pressures. It still remains a question whether 
the water-tube boiler will or can replace the Scotch boiler for 
ordinary service on steamships. Indeed, it is a question 
whether there is any real profit in carrying steam at very high 
pressure. 

The Belleville Boiler is represented by Fig. 22 ; it con- 
sists essentially of a series of coils of pipe made up with bends 
and elbows around which the products of combustion pass 
on the way to the chimney. At the top there is a steam-drum 
A, connected by two circulating-pipes B and C, with a drum 
D at the bottom. From the mud-drum D a rectangular feed- 
supply runs across the front of the boiler to all the coifs or 
elements of the boiler. Each element is continuous from the 
feed-supply to the steam-drum, and is made up of slightly 
inclined pieces of pipe with horizontal bends or connections 
at the end. The effect is much as though a helical coil were 
flattened into two vertical tiers of pipes. The amount of 
water in the boiler is so small that it cannot be run without 



TYPES OF BOJLEKS. 



3' 



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32 



STEAM-BOILERS. 



an automatic feed-water regulator, which in turn requires the 
attention of an expert feed-water tender. The several ele- 
ments deliver a mixture of water and steam to the steam- 
drum, which does not appear to act efficiently as a separator, 
as an external separator is placed between the boiler and the 
engine. The feed-water is supplied to the steam-drum and 
passes through the external circulating-pipes to the mud- 
drum, where it deposits much of its impurities. 




Fig. 23. 

Thornycroft Boiler. — The boiler represented by Figs. 23 
and 24 was built for the torpedo-boat destroyer, " Daring," 
by Mr. Thornycroft ; boilers of slightly different forms have 
been fitted by him, in torpedo-boats and steam-launches. 

The boiler consists essentially of a large drum or sepa- 



TYPES OF BOILERS. 



33 



rat or at the top and three drums at the bottom, connected 
by a large number of bent-tubes. There is, inside of the 
casing, a large tube connecting the top drum to the middle 
drum at the bottom, and this drum is connected to the side 
drums by smaller pipes. The circulation is down from the 
top drum to the middle lower drum, and from that to 
the side drums, then up through all the bent water-tubes to 
the upper drum, where mingled water and steam is delivered 




Fig. 24. 

against a baffle-plate above the water-line. Steam is drawn 
from a nozzle at the rear end of the top drum. 

The arrangement of grates and fire-doors is shown in 
elevation and section by Fig. 23. The middle drum divides 
the grate into two parts; over that drum is a space which is 



34 STEAM-BOILERS. 

in communication with the uptake, as shown by Fig. 24. 
The products of combustion pass among the tubes lead- 
ing from the middle drum ; the tubes to the outer drums 
intercept the radiant heat which would otherwise strike on 
the boiler-casing. 

The boiler-setting is an iron frame, and the casing is thin 
plate iron lined with incombustible non-conducting material. 
There are numerous doors through the casing for cleaning 
the tubes. 

This boiler has proved very successful with a forced 
draught, making steam freely and giving little trouble. The 
boiler contains so small an amount of water that steam may 
be raised quickly, and any demand for steam can be quickly 
met. On the other hand, the feed-supply must be regulated 
with care and skill, and the pressure is liable to fluctuate. 

The Yarrow Boiler. — The form of boiler used by Mr. 
Yarrow for torpedo-boats, is shown by Fig. 25. It resem- 
bles in general arrangement a form used by Mr. Thorny- 
croft with one grate. It, however, differs radically in certain 
particulars, namely, in that the tubes are straight and that 
they enter the upper drum below the water-line, and in that 
there are no pipes outside the casing to carry water from the 
upper drum to the lower drum or reservoirs. Some of the 
tubes.- deliver water and steam to the upper drum, from which 
steam is drawn ; other tubes carry water from the upper 
drum to the lower drums. A given tube may act sometimes 
in one way and sometimes in the other. Naturally those 
tubes which receive the most heat and make the most steam 
deliver to the upper drum, and tubes that receive less heat 
carry down water. 

The air for the fire is drawn from an iron box or casing 
outside the boiler-casing, so that the heat escaping from the 
boiler-casing is largely carried back to the fire, and the fire- 
room, and also the rest of the vessel, is heated up less. 

The Almy Boiler. — This boiler, which is represented by 



TYPES OF BOILERS. 



35 



Fig. 26, is made of short lengths of pipe screwed into return- 
bends and into twin unions. At the bottom is a large tube 
or pipe forming three sides of a square at the sides and back 




YARROVy BOILER 
Fig. 25. 
of the grate. From this water-space the tubes lead into a 
similar structure at the top. The steam and water are dis- 
charged into a separator in front of the boiler, from which 



36 



S TEA M-B OILERS. 



steam is drawn; while the water separated therefrom, together 
with the feed-water, passes down through circulating-pipes to 
the bottom of the boiler. 

The boiler is provided with a coil feed-water heater 




Fig. 26. 



above the main boiler. It is enclosed by a casing lined with 
non-conducting material. It is intended for general marine 
work. 



CHAPTER II. 
FUELS AND COMBUSTION. 

THE fuels used for making steam are coal, coke, wood, 
charcoal, peat, mineral oil, and natural and artificial gas. 
Various waste and refuse products, such as straw, sawdust, 
and bagasse, are burned to make steam. 

All coals appear to be derived from vegetable origin, and 
they owe their differences to the varying conditions under 
which they were formed or to the geological changes which 
they have undergone. 

Anthracite Coal consists almost entirely of carbon and 
inorganic matters; it contains little if any hydrocarbon. 
Some varieties, for example certain coals found in Rhode 
Island, appear to approach graphite in their characteristics, 
and are burned with difficulty unless mixed with other coals. 
Good anthracite is hard, compact, and lustrous, and gives a 
vitreous fracture when broken. It burns with very little 
flame unless it is moist, and gives a very intense fire, free 
from smoke. Even when carefully used, it is liable to break 
ud under the influence of the high temperature of the furnace 
when freshly fired, and the fine pieces may be lost with the 
ash. 

Semi-anthracite or Semi-bituminous Coal is intermedi- 
ate in its properties between anthracite coal and bituminous 
coal; it contains some' hydrocarbon, is less dense than anthra- 
cite, it breaks with a lamellar fracture, and it burns readily 
with a short flame. 

37 



38 STEAM-BOILERS. 

Bituminous Coals contain a large and varying per cent 
of hydrocarbons or bituminous matter. Their physical prop- 
erties and behavior when burning, vary widely and with all 
intermediate gradations represented, so that classification is 
difficult. Three kinds may, however, be distinguished, as 
follows : 

Dry bituminous coals, which burn freely and with little 
smoke and without caking. 

Caking bituminous coals, which swell up, become pasty, 
and cake together in burning. They are advantageously used 
for gas-making, 

Long -flaming bituminous coals, which have a strong ten- 
dency to produce smoke ; some do and some do not cake 
while burning. 

Coke is made from bituminous and semi-bituminous coal 
by driving off the hydrocarbons by heat. Coke made as a 
by-product in gas retorts, is weak and friable, and has little 
value for making steam. Coke made in coking ovens, by 
partial combustion of the coal which is coked, is of a dark- 
gray color, porous, hard, and brittle. It has a metallic lustre, 
and gives out a slight ringing sound when struck. Sulphur 
in the coal may be burned out in coking, if the coal is moist 
or if steam is supplied during coking, so that coke may be 
comparatively free from this noxious element even when made 
from a poor coal. Coke burns without flame and makes a 
fierce fire when forced. 

Lignite, or brown coal, is of more recent geological 
formation than coal, and is in a manner intermediate between 
coal and peat. It frequently contains much moisture and 
mineral matter. It is used where good coal is difficult to get, 
and while the better varieties form a useful fuel, the poorer 
qualities have little value. 

Peat, or turf, is obtained from bogs. It consists of 
slightly decayed roots of the swamp vegetation mingled with 
more or less earthy matter. For domestic use it is cut and 



FUELS AND COMBUSTION. 39 

dried in the air. It is little used for making steam, though 
when pulverized, dried, and compressed it makes a useful 
artificial fuel. 

Wood is used for making steam either in remote places 
where coal is hard to get and timber is plenty, or where saw- 
dust or other refuse wood is produced in quantity in manufac- 
turing operations. Wood is also used for kindling coal-fires. 
One cord of hard wood is equivalent to one ton of anthracite 
coal ; one cord of yellow-pine is equal to half a ton of coal ; 
other soft woods are, as a rule, of less value for fuel. 

Charcoal is made by charring wood ; it is but little used 
for making steam. 

Mineral Oil, in the form of crude petroleum or the refuse 
heavy oil left from the distillation of petroleum, is used for 
making steam, especially in the neighborhood of the Black 
Sea oil-field, and by steamers carrying oil from those fields. 
It is customary to throw the oil into the furnace in the form 
of finely divided spray through special spraying apparatus 
worked either with compressed air or with superheated steam. 
The use of superheated steam has its convenience only to 
recommend it, for it adds to the inert material to be uselessly 
heated. Special precautions must be taken, when petroleum 
is burned, to avoid flooding the furnace with oil and to pre- 
vent explosions of the vapor and burning of the oil in tanks 
or receptacles. 

Gases. — Natural gas from gas-wells has been used for 
making steam, usually in a crude and wasteful way. Some 
attempts have been made to use gas made from poor and 
smoky coal, in producer-furnaces like those used in metallurgi- 
cal operations ; but the gain to be expected is only the sup- 
pression of the smoke nuisance, which is rather a social than 
an economical problem. 

Artificial Fuels. — The small waste from coals and char- 
coals, sawdust, and other fine combustible material which 
cannot be sold in such shape, is sometimes made into cakes or 



40 



S TEA M-BOILERS. 



briquettes by mixing it with some adhesive material and then 
compressing it. The adhesive materials have been wood-tar, 
coal-tar, or else clay. Tar is available in limited quantities 
only, and clay is disadvantageous since it adds to the inert 
material, of which fine fuel is liable to have an excess. 
Artificial fuels have some advantages for special purposes, and 
can be stored compactly ; they are used mostly where good 
fuel is difficult to get. 

Composition of Fuels. — The composition of a number 
of American coals, together with the total heat of combustion 
by Dulong's formula, is given in the table on page 41, which 
has been kindly furnished by Mr. Henry J. Williams. These 
results are a part of a very extended investigation by Mr. 
Williams, to be published in full in the near future. Most 
of the results are the averages of several separate analyses, and 
all may be depended upon to give a fair representation of the 
coals named. 

Analyses by Mahler of various European coals and of a 
few American coals, together with the total heat of combus- 
tion, are given in the table on page 42. 

The following table gives the composition of several rep- 
resentative petroleums : 

COMPOSITION OF PETROLEUMS. 



Pennsylvania, crude 

Caucasian, light. . . . 

heavy . . 

Petroleum refuse. . . 



Carbon. 


Hydrogen. 


Oxygen. 


84.9 


13-7 


1.4 


S6.3 


13 6 


O.I 


86.6 


12. 3 


I. I 


87.1 


11.7 


I .2 



Specific 
Gravity. 



0.8S6 

0.884 
0.938 
0.938 



Heat of Combustion. — The number of thermal units de- 
veloped by the complete combustion of one unit of weight of 
a fuel is called the heat of combustion. It can be determined 
by burning the fuel in a properly constructed calorimeter. 
The most recent and best results are those obtained by the 
use of Mahler's bomb-calorimeter. This is a strong recep- 



FUELS AND COMBUSTION. 



41 



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-r 


m 



in r^co 

O CO <N 

o f^ in 
r^ r^ r> 



jo 9Aisnp 



co CM in coo 



T in 

co ct> 


o 

in 


0> 

T 



•qsy 


885,88 


o o o o 
o o o o 
r^ o o O 


OOO 
OOO 

h -r o 


O O 
in in 


co O O 
co m cm 
co t^ O 


OOO 
OOO 
CM CM O 




in T in ino 


m tuiT 


t co 


TO 


OOO 


T co in 


OldODS 

-ojpAH 


O O O m O 
in o O r^O 
T r»co r~» r» 

n4fi h h 


O m O O 
in w O in 

coo w cm 


ooo 
ooo 
cm o o 

l-H co O* 


O T 

►H T 

O* co 


O O m 
-1- CM cm 

o o' o 


883 

in in cm 

o* 6 6 


- U9Soj; 
-IN P u e 
uaSAxQ 


O s i- 1 inco 
OvO co O r->. 
«- C* r* O cm 


tO O - N 

co TO to 
co <n r^ T 


co coco 
i-. « O 


co O 

o o 

co r- 


ooo 

CO O co 
r^ co cm 


O^ in O 
NtO i- 
O in i-h 


N CM CM inO 


T in in in 


r^co in 


T in 

CM. CM 


O O T 
co T co 


CM ►-< CM 



•uaSojpAH 



in i^ co cm O 

OO co O - 1 
O co t^co O 



Oco in cm 
co Ceo r-» 
i-i hh co i^ 



T T T T 



O in O 
co TO 
O CM O 



T co in 
-1- coco 

TO O 



•uoqivj 



O TO co o co r^. TO to n n 
ino T cm T r^coinT mooco 
Tmt^or^l TO^r^inl t«co 



O O co nn o 
O -too cm co co 
co t i-i I r^ in o 



rt c c 






in 
C ^ 

= b£Es 
^222 



gguu 
2 u u o 



L u u u u 
< < C/5 C/5 C/) 



W 



c c 
<< c 

B S"g 

I- J- < 



o o 

c c 



° 2 



3 3 O O 
.■3 .3 C C 

5 Sal 

S S 2 2 



§E 
«<u o g 

S 6 13 

o o c 

o o G 
W« 
tn t/i be 



*? 

s s 

o p 



J-J 



<u T o 
E ' GQ 

'5. - - 

rj E 
c 1 o 

S P i- 

S = 3 
O <u O 

2UH 



5 g rt 

u c.2 

be c 

ij E as 

a; .3 ^ 

e-9 s 



o o 
UU 



FUELS AND COMBUSTION. 43 

tacle of wrought iron or bronze, gold-plated or enamelled 
inside. The fuel to be tested is placed in a small platinum 
crucible, with an arrangement for igniting by electricity. 
The bomb is then filled with oxygen under the pressure 
of about twenty-five atmospheres, and is placed in a calo- 
rimeter-can containing water. There is oxygen in excess, so 
that the charge when ignited is completely consumed, and 
the resultant total heat of combustion is absorbed by the 
metal of the bomb and by the water in the calorimeter. The 
corrections for the calorimeter are determined by burning in 
it, some substance like naphthaline, for which the heat of com- 
bustion is known. The processes of making combustion 
determinations are simple and direct; the difficulties are those 
incident to accurate measurements of temperatures, for which 
purpose the best physical thermometers are required. The 
experimenter must be an expert physicist, who has had expe- 
rience in the use of the apparatus. The table of composi- 
tion of fuels by Mahler * gives also the total heats of the 
fuels, determined by the same experimenter by aid of the 
bomb-calorimeter. 

An engineering expert who has had adequate training in 
a physical laboratory, may learn how to make determinations 
of the total heat of combustion; an engineer in general prac- 
tice will find it advantageous to refer such work to an expert 
physicist. It is not too much to say that all crude forms of 
apparatus for finding total heat of combustion of fuels are 
useless and misleading. 

The heats of combustion of carbon in various forms as de- 
termined by Berthelot f are : 

Diamond 7859 calories. 

Diamond bort 7860. 9 ' ' 

Graphite 790 1.2 ' ' 

Amorphous from wood........ 8137.4 " 

* Bulletin de la Soc. d'Encouragement pour Industrie nationale, 1891. 
■r Comptes rendu, 1889. 



44 STEAM-BOILERS, 

The heat of combustion of carbon in fuels may be taken at 
8140 calories, a calorie being defined as the heat required 
to raise one kilogram of water from I5°C to 16 C. This 
will give in the English system of units 14650 British thermal 
units, the B. T. U. being defined as the heat required to raise 
the temperature of a pound of water from 62 F. to 63 F. 
These definitions are founded on Rowland's determination of 
the mechanic equivalent of heat ; the difference between them 
and others commonly given are not of practical importance 
in this connection. 

The following table gives the heat of combustion of some 
elements and simple gases : 

Carbon burned to C0 2 8, 140 calories ; 14,650 B.T.U. 

Carbon burned to CO 4,400 

Hydrogen 34,500 " 62,100 

Sulphur 4,032 

Marsh-gas, CH 4 , C 23,513 

defiant gas, C. 2 H 4 , 21, 343 

Carbon monoxide. 4, 393 

Chemistry of Combustion.— Calculations concerning the 
heat of combustion of fuels and the amount of air needed for 
combustion, require a knowledge of the elements of chemistry. 

Elementary chemical substances are those that have not 
been decomposed, such as oxygen, hydrogen, and nitrogen. 
The elements enter into chemical combination in fixed propor- 
tions by weight ; these proportions are called the combining 
weights or the atomic weights of the elements. In the following 
table are given the most important chemical elements of fuels, 
their chemical symbols, and their atomic weights. The table 
gives other useful information which will be referred to later. 

A chemical combination, such as water, is represented by 
a formula consisting of the symbols of the elements entering 
into the combination, each symbol having a subscript which 
shows the number of times the combining or atomic weight of 



FUELS AND COMBUSTION. 



45 



Carbon 

Hydrogen 

Oxygen 

Nitrogen 

Sulphur 

Carbon dioxide . . 
Carbon monoxide. 

Water 

Air 

Ash 



Symbol or 
Composi- 
tion. 



c 

H 

O 

N 
S 

co 2 

CO 

H,0 



Atomic or 

Molecular 

Weight. 



12 

I 

16 

14 
12 

I2 + 2X 
12 -f- l6 
2+16 



1 6 



Specific 
Volumes. 





I7S.8SI 

11.2070 

12.7561 

8.10324 
12.81 


12 


3909 



Specific 
Heat in 
Gaseous 

Condition, 



3-409 
O.2175 

O.243S 

O.2169 
O.2450 
0.4805^ 
O.2375 
0.2 



Density or 

Weight of 

One Cubic 

Foot. 



0.005590 

O.08928 

O.07837 

o. 12341 

O.07806 
O.08071 



* Superheated steam. 

the element occurs in the combination. This water is repre- 
sented by 

H,0, 

which indicates that water is made up of two portions oi hy- 
drogen and one portion of oxygen. It is commonly said that 
two atoms of hydrogen and one atom of oxygen unite to form 
one molecule of water. As the atomic weight of hydrogen is 1 
and the atomic weight of oxygen is 16, we have water formed 
of two pounds of hydrogen to 16 pounds of oxygen. 

Again, carbon may unite with one portion of oxygen to 
form carbon monoxide or carbonic oxide, represented by CO ; 
or carbon may unite with two portions of oxygen to form 
carbon dioxide or carbonic acid, represented by C0 2 . Re- 
ferring to the table on page 44, it appears that the complete 
combustion to CO., gives more than three times the heat ob- 
tained from incomplete combustion to CO. But the resulting 
gas, CO may be burned with one more portion of oxygen, and 
will finally form CO a . Assuming that the double process will 
yield the same amount of heat per pound of coal as is ob- 
tained by direct combustion to C0 2 , we may calculate the 
heat of combustion of one pound of carbon monoxide as fol- 
lows : 



4° 5 TEA M-B OILERS. 

In the combustion of carbon to CO, 12 pounds of carbon 
unite with 16 pounds of oxygen, forming 28 pounds of CO; 
hence one pound of carbon will form 

H±i^ = 2i lbs. Of CO. 
12 

The heat developed by burning these 2-J- pounds of carbon 
monoxide, under our assumption, is 

14650 — 4400 = 8250 B. T. U., 

so that each pound of carbon monoxide will yield 

8250 -i-2i = 4393 B. T. U., 

as given in the table on page 44. 

The complete combustion in either case will give 

12 + 2 X 16 _ % 

pounds of carbon dioxide for each pound of carbon. 

Calculation of Heat of Combustion.— If a fuel were a 
mechanical mixture of two chemical elements such as carbon 
and sulphur, the heat of combustion could obviously be found 
by calculating the parts separately and adding the results. For 
example, a mixture of 60 per cent carbon and 40 per cent 
sulphur would give 

0.60 X 14650 = 8790.0 
0.40 X 4032 = 1612.8 

10402.8 B. T. U. 

for each pound of the mixture. 

Fuels, as a rule, contain carbon in a free state, and various 
compounds of carbon and hydrogen, and compounds of carbon, 
hydrogen, and oxygen. Now the rapid union of chemical ele- 
ments is usually accompanied by the evolution of heat, as in 



FUELS AND COMBUSTION. 47 

the combustion of oxygen and hydrogen. Conversely, heat is 
required to break up a chemical combination. Now the com- 
bustion of a fuel is a complex process, involving usually some 
breaking up of chemical compounds and the union of chemical 
elements with oxygen ; the exact nature of the process is far 
from certain even when the real chemical compounds and ele- 
ments of which the fuel is composed are known. As a rule we 
know only the final analysis of the fuel and do not know the 
compounds which enter into it. For this reason the only 
true way of determining total heat of combustion is by experi- 
ment. Nevertheless it is customary and convenient to make 
a calculation of the total heat of combustion by an arbitrary 
method, when the real heat of combustion of a fuel has not 
been determined. 

Dulong proposed that the heat of combustion should be 
calculated on the assumption that the oxygen in the fuel and 
enough hydrogen to unite with it and form water, could be set 
aside as inert, and that the remainder of the hydrogen and all 
the carbon could be treated as free elements. From the com- 
position of water and the atomic weights of hydrogen and 
oxygen it is clear that each pound of oxygen will require 

2X1 i 



16 8 

of a pound of hydrogen. Dulong's method may therefore be 
expressed by the equation 

Total heat = 14,6500 + 62, 100 (H — JO) 

in which the letters C, H, and O represent the weights of car- 
bon, hydrogen, and oxygen in one pound of fuel. No con- 
fusion need arise because the letters are used with a different 
significance from that given them in chemical formulae. This 
equation does not give very satisfactory results. 



48 STEAM-BOILERS. 

Mahler has proposed an empirical formula for finding- 
heats of combustions which in French units is 

Total heat = 8140 C + 34,500 H — 3000 ( O + N), 

in which C, H, O, and N represent the weights of the ele- 
ments carbon, hydrogen, oxygen, and nitrogen in a kilogram 
of fuel. The result is in calories. 

In English units Mahler's equation becomes 

Total heat = 14,650 C ~f 62, 100 H — 5400 (O + N), 

in which the letters represent the weights of the correspond- 
ing elements in one pound of the fuel. The result is in 
B. T. U. This equation gives results that agree very well 
with Mahler's experimental determinations, as shown by the 
table on page 42. 

For example, the total heat of combustion of Pittsburg 
bituminous coal, for which the ultimate analysis in the table 
on page 41 gives 

= 0.7647, H = 0.0519, O — 0.0810, N = 0.0145. 

appears by Dulong's formula to be 

14650 C + 62, 100 (H - i O) 

^ , x- / 0.0810 
= 14,650 X 0.764; + 62, 100 f 0.05 19 _ 

■ = 13,800 B. T. U. 

Mahler's formula for the same coal gives 

14,650 C + 62, 100 H — 54,000 (O + N) 
= 14,650 X 0.7647 -f 62, 100 X 0.05 19 

— 5400(0.0810+ 0.0145) 
= i3, 9 ioB.T.U. 

Air required for Combustion. — If the moisture and car- 
bon dioxide in the air be neglected, and if, further, the argon 



FUELS AND COMBUSTION. 49 

is not distinguished from the nitrogen, then we have for the 
composition of the atmospheric air, 

_, . . 1 ( Oxygen 0.2 32 

By weight „/ 5 * 

J I Nitrogen 0.768 

_ , ( Oxygen o. 2004 

By volume K T . J Z 

( Nitrogen 0.7906 

For rough calculations it is customary to consider that the 
atmosphere is made up of one volume of oxygen and four 
volumes of nitrogen. This approximation is sufficient for 
calculation of air required by fuels, and for similar purposes. 

The air required for combustion of a given fuel may be 
estimated from its composition and from the composition of 
the air. A few examples will make the process clear. 

Thus, carbon burned to C0 2 requires two portions of 
oxygen, so that one pound of carbon will require 

2 X 16 

-J2—- 2 * 

pounds of oxygen. Since air is 0.232 part oxygen by weight, 
one pound of carbon will require 

2|-t- 0.232 — 11. 5 

pounds of air for complete combustion. 

In like manner one pound of hydrogen will require 

2 

pounds of oxygen, or 

8 -f- 0.232 = 34.5 

pounds of air for complete combustion. 

Another method of calculation is based on the approxi- 
mate composition of air, i.e., one volume of oxygen and four 
of nitrogen. This method depends on the fact that the 



5 O S TEA M-B OILERS. 

weights of a cubic foot of different kinds of gases are propor- 
tional to their atomic weights ; so that if the weight of a cubic 
foot of hydrogen be taken for the basis of comparison and be 
called unity, then the weight of a cubic foot of oxygen will 
be 16, while that of nitrogen will be 14. We shall then have 
for the approximate composition of air one volume of oxygen 
having the weight 16, and four volumes of nitrogen having each 
the weight 14. In order to get one pound of oxygen we 
must take 

(16 + 4 X 14)-^- 16 = 4J 

pounds of air. 

It has already been shown that one pound of carbon will 
require 2§ pounds of oxygen. By the method just stated it 
appears that a pound of carbon will require 



,2 



X 4i = I2 



pounds of air. This result is often quoted and is easily 
remembered. 

Since a pound of hydrogen requires 8 pounds of oxygen, 
this method gives 

3 X 4i = 36 

pounds of air for each pound of hydrogen. 

In calculating the air required for a fuel it is customary to 
use the convention proposed by Dulong for finding heat of 
combustion, namely, that each pound of oxygen in the fuel 
renders one eighth of a pound of hydrogen inert, and that the 
remainder of the hydrogen and all the carbon can be treated 
as free elements. In using this convention it is customary to 
take the approximate weights of air just calculated for a 
pound of carbon and a pound of hydrogen. The convention 
can then be stated in the form of an equation as follows: 

Air per pound of fuel = 12 C + 3^ (H — . \ O), 



FUELS AND COMBUSTION. 5 1 

in which the letters C, H, and O represent the weights of 
carbon, hydrogen, and oxygen in one pound of the fuel. 
An application of this equation to Pittsburg coal gives 

/- , <rt 0.08 IO\ 

Air = 12 X 0.7647 + 36(0.0519 — I = 10.7 pounds. 

This result is somewhat larger than would be obtained were 
the more exact composition of the atmosphere given on page 
49 used, together with the assumption that the oxygen ren- 
ders inert its equivalent of hydrogen ; but the method is not 
sufficiently well grounded to warrant much refinement. 

As a further illustration of the method the following cal- 
culation of the air required for one pound of olefiant gas may 
be interesting. This gas, having the composition C a H 4 , con- 
sists of 

2 X 12 5 

— ■ = - carbon, 

2 X 12 +4 X 1 7 

4Xi 1 , , 

= - hydrogen, 



2 X 12+4X 1 7 
and will require 

f X 12 + | X 36 — 1 5.4 pounds of air. 

Air for Dilution. — In order to secure complete combustion 
of coal in the furnace of a boiler it is necessary to supply an 
excess of oxygen, or, what amounts to the same thing, an 
excess of air. This excess varies from one half the quantity 
required for combustion to an equal quantity. Thus, roughly, 
from 18 to 24 pounds of air may be furnished per pound of car- 
bon and from 54 to 72 pounds of air per pound of hydrogen. 

Volume of Air for Combustion. — The table on page 45 
gives the density or weight of one cubic foot of the several 
gases mentioned, also the reciprocal of the density, or the 
volume occupied by one pound of the gas. This is called the 
specific volume of the gas. The specific volume of air is 
12.3909 at the pressure of the atmosphere and at the temper- 



With 50 per 
cent Dilution. 


With 100 per 
cent Dilution. 


225 


3OO 


675 


9OO 



52 S TEA M-B OILERS. 

ature 32 F. The volume of a pound of gas increases as the 
temperature rises. At 6o° F. one pound of air will occupy- 
about 13 cubic feet. To find the volume of air required per 
pound of fuel we may simply multiply the weight by 13, for 
ordinary calculations. Thus we shall have for the air per 
pound of the principal elements in fuels : 

Without 
Dilution. 

Carbon 150 

Hydrogen 450 

These approximate values are sufficient for determining 
the dimensions of doors or passages through which air is 
supplied to the fire. 

This method applied to Pittsburg coal will give, approxi- 
mately, 

ioX'i3= J 30 

cubic feet of air for each pound of coal without dilution. 
With dilution of 50 per cent the air required will be about 
200 cubic feet for each pound. 

Sometimes, in connection with boiler-tests or for other 
purposes, a more exact estimate of the amount of air is de- 
sired. The calculation for this purpose can be best explained 
by aid of an example. 

Example. — Required the weight and volume of air needed 
for combustion of Pittsburg coal with 50 per cent dilu- 
tion, the temperature of the atmosphere being 70 F. and 
the height of the barometer being 29 inches, when reduced 
to 32 F. 

This coal is composed of 76.47 per cent carbon, 5.19 per 
cent hydrogen, and 8.10 per cent oxygen. Assuming that 
the oxygen renders inert one eighth of its weight of hydrogen, 
there will be available 

8.10 

5. 19 —- = 4. 18 per cent 

o 



FUELS AND COMBUSTION. 53 

of hydrogen and 76.46 per cent of carbon. Since one pound 
of carbon requires 2*% pounds of oxygen, and one pound of 
hydrogen requires 8 pounds, the weight of oxygen required 
per pound of coal is 

2| X 0.7646 + 8 X 0.0418 = 2.374 pounds. 

But air contains 23.2 per cent of oxygen by weight, so that the 
air required per pound of coal is 

2.374 4- 0.232 = 10.2 pounds. 

The specific volume of air is 12.39, so that each pound of 
coal will require 

10.2 X 12.39 = I2 6 

cubic feet of air at the normal pressure of the atmosphere 
and at 32 ° F. 

To find the volume of air required at the actual pressure 
of the atmosphere and the actual temperature, we have the 
facts that the volume of a given weight of air is inversely pro- 
portional to the absolute pressure and directly proportional 
to the absolute temperature. Now the absolute pressure of 
the atmosphere is 29 inches of mercury as given by the 
barometer, while the normal pressure is 29.92 inches of mer- 
cury. To get the absolute temperature we add 460.7 to the 
temperature by the thermometer; the absolute temperature 
of 32 F. is 492.7, and that of 70 F. is 530.7. -Under the 
conditions of the problem the air required per pound of fuel 
will have the volume, without dilution, of 

- $30.7 2Q.Q2 

126 X — — - X -?-2- — 140 
492.7 29.00 

cubic feet. With 50 per cent dilution the volume will be 
206.5 cubic feet. 

Determination of Air per Pound of Coal.— The amount 
of air supplied per pound of coal may be determined either by 



54 STEAM-BOILERS. 

measuring the air supplied to the furnace or by an analysis of 
the products of combustion. 

For the first method the following arrangement has been 
used in boiler-tests at the Massachusetts Institute of Tech- 
nology : The ash-pit doors are removed and a sheet-iron 
mouthpiece is fitted over the opening into the ash-pit. The 
air for combustion is supplied by a cylindrical sheet-iron con- 
duit leading into this mouthpiece. The area of the conduit 
should be at least equal to the area of the fire-door or fire- 
doors, and its length should be several times its diameter. 
The velocity of the air in the conduit is measured by an ane- 
mometer, from which the volume of air is readily calculated, 
and its weight determined from the temperature and pressure of 
the atmosphere. The joint between the mouthpiece and the 
furnace front must be luted to avoid leakage, and leaks or ad- 
mission of air to the furnace otherwise than through the sheet- 
iron conduit must be stopped or allowed for. Anemometers, 
even when tested and rated, are liable to be affected by errors 
of two per cent or more. They are commonly tested by 
swinging them on a revolving arm through still air — a method 
that is proper for small or moderate velocities, but difficult to 
use, and is vitiated by the action of centrifugal force at high 
speeds. An ideal way of testing an anemometer would be to 
find its reading in such a conduit when the weight, and con- 
sequently the velocity, of the air per second is known. The 
weight may be determined by causing the supply of air to 
flow through a well-rounded orifice, to which calculations by 
the proper thermodynamic equations may be applied. This 
method for large conduits would involve the use of a very large 
air-compressor, which makes it hardly practicable. 

Orsat's Gas Apparatus. — This apparatus, which is well 
adapted to the analysis of flue-gases, determines the propor- 
tion by volume of the carbon dioxide, carbon monoxide, and 
oxygen in a mixture of gases. The remainder of tne flue- 
gases is commonly assumed to be nitrogen, but it includes 



FUELS AND COMBUSTION. 



55 



unburned hydrocarbon, if there be any, and steam or vapor 
of water. In Fig. 27, A, B, and Care pipettes containing, 
respectively, solutions of caustic potash to absorb carbon diox- 
ide, pyrogallic acid and caustic potash to absorb oxygen, and 
cuprous chloride in hydrochloric acid to absorb carbon mon- 
oxide. 

At W is a three-way cock to control the admission of gas 
to the apparatus ; at D is a graduated burette for measuring 
the volumes of gas, and at P is a pressure-bottle connected 
with D by a rubber tube to control the gases to be analyzed. 
The pressure-bottle is commonly filled with water, but glyc- 




Fig. 27. 



erine or some other fluid may be used when, in addition to the 
gases named, a determination of the moisture or steam in the 
flue-gases is made. 

The several pipettes A, B, and C are filled to the marks a, 
by and c with the proper reagents, by aid of the pressure-bottle 
P. With the three-way cock W open to the atmosphere, the 
pressure-bottle P is raised till the burette D is filled with 
water to the mark m ; communication is then made with the 
flue, and by lowering the pressure-bottle the burette is filled 
with the gas to be analyzed, and two minutes are allowed 
for the burette to drain. The pressure-bottle is now raised 
till the water in the burette reaches the zero-mark and the 



56 



STEAM-BOILERS. 



clamp k is closed. The valve W\s now opened momentarily 
to the atmosphere to relieve the pressure in the burette. Now 
open the clamp k and bring the level of the water in the pres- 
sure-bottle to the level of the water in the burette, and take 
a reading of the volume of the gas to be analyzed ; all readings 
of volume are to be taken in a similar way. Open the cock 
a and force the gas into the pipette A by raising the pressure- 
bottle, so that the water in the burette comes to the mark m. 
Allow three minutes for absorption of carbon dioxide by the 
caustic potash in A, and finally bring the reagent to the mark 
a again. In this last 'operation, brought about by lowering 
the pressure-bottle, care should be taken not to suck the 
caustic reagent into the stop-cock. The gas is again measured 
in the burette and the diminution of volume is recorded as the 
volume of carbon dioxide in the given volume of gas. In like 
manner the gas is passed into the pipette B, where the oxygen 
is absorbed by the pyrogallic acid and caustic potash ; but as 
the absorption is less rapid than was the case with the carbon 
monoxide, more time must be allowed, and it is advisable to 
pass the gas back and forth, in and out of the pipette, several 
times. The loss of volume is recorded as the volume of 
oxygen. Finally, the gas is passed into the pipette C, where 
the carbon monoxide is absorbed by cuprous chloride in hydro- 
chloric acid. 

The solutions are as follows : 

A. Caustic potash, I part; water, 2 parts. 

B. Pyrogallic acid, i gramme to 25 c.c. caustic potash. 

C. Saturated solution of cuprous chloride in hydrochloric 

acid having a specific gravity of 1. 10. 

The absorption values per cubic centimetre of the reagents 

A Caustic potash absorbs 40 c.c. carbon dioxide. 

B. Pyrogallate of potassium absorbs 22 c.c. oxygen 

C. Cuprous chloride absorbs 6 c.c. carbon dioxide. 



are- 



FUELS AND COMBUSTION. 57 

Samples of gas for analysis by Orsat's apparatus should be 
taken from the back of the furnace, from the uptake, and from 
the chimney; the difference in composition of gases at the 
several points will give the basis for calculations of leakage. 

When it is not convenient to draw gases from the flue di- 
rectly into the measuring burette of the apparatus, samples of 
gas may be drawn into glass bottles with rubber stoppers, from 
which gas can be supplied to the burette. 

Calculation from a Gas Analysis. — The calculation of the 
amount of air supplied per pound of carbon and per pound of 
coal, from the known chemical constituents of the flue-gases, 
is best shown by an example. 

Example. — Let it be assumed that the analysis of the flue- 
gases resulting from the burning of Pittsburg bituminous coal 
gives by volume 13 per cent of carbon dioxide, 0.5 per cent 
of carbon monoxide, and 6 per cent of oxygen. It is con- 
venient to treat the percentages by volume as the number of 
cubic feet of the several gases in one hundred cubic feet of flue- 
gas. We will thus have — 

^ Density. 

L,as - Volume. (See page 45.) Weight. 

Carbon dioxide 13 o. 12341 1.6043 

Carbon monoxide 0.5 0.07806 0.03903 

Oxygen.... .,,.... 6 0.08928 0.53568 

Now one pound of carbon dioxide is composed of 

2 X 16 8_ 

12 -\- 2 x 16 11 

of a pound of oxygen and 3/1 1 of a pound of carbon, and a 
pound of carbon monoxide is composed of 

16 4 



12 -f- 16 7 

of a pound of oxygen and 3/y of a pound of carbon. Conse- 
quently we have 



58 STEAM-BOILERS, 

T \ X 1.6043 = 1. 1668 T 3 T X 1.6043 =0-4375 

4 x 0.03903 = 0.0223 f x 0.03903 = 0.0167 

o-5357 



Pounds of oxygen, 1.7248 Pounds of carbon, 0.4542 

And as air consists of 0.232 part by weight of oxygen, the air 
per pound of carbon from the gas analysis is 

1.7248 £■ J 

— - — - — -- 0.232 = 10.4 pounds. 
0.4542 

The coal in question contains 76.47 per cent of carbon, 5.19 
per cent of hydrogen, and 8. 10 per cent of oxygen. Of these 
elements Orsat's apparatus accounts for the carbon only ; the 
oxygen and hydrogen together with unburned volatile matter 
pass off with the nitrogen. 

The analysis shows 16.4 pounds of air for each pound of 

carbon; consequently the carbon in one pound of coal will 

require 

0.7647 X 16.4 = 12.5 

pounds of air. Assuming that the oxygen in the coal renders 
one eighth of its weight of hydrogen inert, and that the re- 
mainder will require 36 pounds of air per pound of hydrogen, 
we shall have 



36(0. 



0.08 io\ 
0519 o — = J -5 



of a pound of air required for the hydrogen. So that the 
total air per pound of coal is about 

12.5 -j- 1.5 = 14 pounds. 

The calculation just given, involving the use of the densities 
of the several gases, is perhaps the most readily understood ; 
there is another method, which gives the same result and is 
more expeditious, depending on the fact that the weight of a 
gaseous compound referred to hydrogen as unity, is half its 



FUELS AND COMBUSTION. 59 

molecular weight. This quantity is called the vapor density of 
the compound. 

Thus the vapor density of carbon dioxide, C0 2 , is 

£(I2 +2 X 16) = 22; 

and the vapor density of carbon monoxide, CO, is 

1(12 + 16) = 14. 

Assuming as before that in each 100 cubic feet of flue-gases 
there are 13 cubic feet of C0 2 , 0.5 of CO and 6.0 of O, we 
have for the corresponding weights, based upon hydrogen as 
unity, 

13 x 22 = 286 for C0 2 

0.5X 14= 7 for CO 

6.0 x 16= 96 for O 

Total, 389 

The last result depending on the fact already noted, that the 
weights of elementary gases are proportional to the atomic 
weights. 

Now each pound of C0 2 contains 3/1 1 of a pound of carbon, 
and each pound of CO contains 3/7 of a pound of carbon, so 
that of the 287 parts by weight of C0 2 we shall have 

-f T X 2S6 = 78 

parts of carbon, and of the 7 parts by weight of CO we shall 
have 

f X 7 = 3 
parts of carbon. The total weight of carbon will be 

78-1-3 = 81. 

The weight of oxygen is clearly 

389 — 81 = 308. 



60 STEAM-BOILERS. 

The oxygen per pound of carbon is therefore 

308-81 = 3.85, 

and the air per pound of carbon is 

308 . 

— -0.232 = 16.4 

pounds, as found by the previous calculation. 

Loss from Incomplete Combustion.— The presence of 
even a small amount of carbon monoxide in flue-gases is evi- 
dence of a very appreciable loss of efficiency, as may be seen 
by the following example, quoted from a test made on a 325- 
horse-power boiler at Lowell. The coal used was George's 
Creek Cumberland, fired by hand. 

An analysis of flue-gases by Orsat's apparatus showed 12.5 
per cent of C0 2 , 1.1 per cent of CO, and 4.1 per cent of O, 
by volume. 

Using the method of vapor densities for making the calcu- 
lation, it appears that the C0 2 contained 

T 3 T X 12.5 X 22 = 75 parts of carbon, 
and the CO contained 

f X 1.1 X 14 = 6.6 parts of carbon. 
Now 75 pounds of carbon burned to C0 2 gives 
75 x 14,650 = 1,098,750 B. T. U., 
and 6.6 pounds of carbon burned to CO gives 
6.6 x 4400 = 29,040 B. T. U., 

or a total for all the carbon of 1, 127,790 B. T. U. 

Had all the carbon been burned to C0 2 , the heat of com 
bustion would have been 

(75 + 6.6) 14,650 = 1, 195,440 B. T. U. 



FUELS AND COMBUSTION. 6 1 

The loss by incomplete combustion was consequently 

1,195,440—1,127,790 - 

yD ^ ' /y X 100 = 5.6 per cent. 

1,195,440 

The actual loss may be placed at a little less figure than 5.6 
per cent, since less air is required for burning carbon to CO 
than for C0 2 . 

Loss from Excess of Air. — The ideal condition would be 
to supply just enough air to burn all the carbon in the coal to 
C0 3 and all the free hydrogen to H 2 ; it is necessary to use 
somewhat more air than required for complete combustion to 
avoid the formation of CO and the attendant loss of heat. On 
the other hand, too great an excess of air occasions a loss, as 
that excess must be heated to the temperature in the chimney. 

As an example, suppose that Pittsburg coal can be com- 
pletely burned with 50 per cent excess of air, but that 100 per 
cent excess is allowed to pass through the grate. 

To simplify the problem we will neglect the effect of sul- 
phur and of the ash, more especially as it is not certain what 
their effect is ; we know only that it cannot be very impor- 
tant. 

Each pound of carbon will yield 3§ pounds of CO Q and 
each pound of hydrogen will yield 9 pounds of H 2 0. There 
will therefore be 

3s X 0.7674 = 2.8039 pounds of C0 2 ; 
9X0.0519 = 0.4671 " " H 2 0. 

In the calculation for the weight of air (page 45) it has 
been shown that 2.374 pounds of oxygen and 10.2 pounds of 
air are required for combustion. There is therefore 

10.2 — 2.374 = 7.826 

pounds of nitrogen in the air for combustion. But each 
pound of coal contains 0.014 of a pound of nitrogen, so that 
the total nitrogen is 7.840 pounds. 



62 STEAM-BOILERS. 

Now the heat required to raise the temperature of one 
pound of a substance one degree, called the specific heat, is 
given in the table on page 45. For carbon dioxide the specific 
heat is 0.2169, and the heat required to raise 2.8039 pounds 
one degree is 

2.8039 X 0.2169 = 0.6082 B. T. U. 

The following are the calculations for the several compo- 
nents of the products of combustion : 

Weight. Specific 

Carbon dioxide, CO a 2.8039 X 0.2 169 = 0.6082 B. T. U. 

Steam, H a O. 0.4671 X 0.4805 = 0.2244 ii 

Nitrogen 7.840 X 0.2438 = 1. 91 14 " 

Air for dilution 50$.... 5.100 X 0.2375 = 1.2112 " 



Total 3-9552 



If the external air is at 6o° F., and the gases in the chim- 
ney are at 560 F., then the heat in the chimney-gases above 
the temperature of the air is 

500 X 3.9552 = 1978 B. T. U. 

The total heat of combustion of this coal by Dulong's 
formula is 13800 B. T. U. ; of this about 10 per cent will be 
lost by conduction and radiation. There will then remain to 
be transferred to the water in the boiler 

13800 - (1380 + 1978) = 10442 B. T. U. 

This is about y6 per cent of the heat generated by combus- 
tion. 

Suppose that the dilution is allowed to be 100 per cent, 
so that 5 additional pounds of air per pound of coal are ad- 
mitted to the grate. Then to the above total must be added 



FUELS AND COMBUSTION. 63 

1.2 1 12 B. T. U., making in all 5.1664 B. T. U. Multiply- 
ing by 500, the difference of temperature assumed 

500 X 5- 1664 = 2583 B. T. U. 

Assuming, as before, 10 per cent for loss by radiation and 
conduction leaves 

13800 - (1380+2583) = 9837 B. T. U. 

to be transferred to the water in the boiler. This is about 72 
per cent, so that the loss by the excess of dilution is about 4 
per cent. 

Hypothetical Temperature of Combustion, — A calcula- 
tion is sometimes made of the temperature of the fire on the 
assumption that the total heat of combustion is all applied to 
raising the temperature of the products of combustion, includ- 
ing the ash. In the case of Pittsburg coal it has been found 
that 3.9552 B. T. U. are required to raise the products of 
combustion one degree, allowing 50 per cent for dilution. 
This coal has y.6 per cent ash, for which a specific heat of 0.2 
may be allowed. We must therefore add to the total just 
quoted 

.076 X 0.2 = 0.0152 B. T. U., 

making in all 3.9704 B. T. U. Dividing the total heat by 
this quantity, we get 

13800 -=- 3-97°4 = 348o F. 

for the elevation of temperature. To this we will add the 
temperature of the air admitted to the furnace, say 6o° F., 
making 3540 F. for the hypothetical temperature of the 
fire. 

Such a temperature is never reached in the furnace of a 
boiler, for the combustion is not instantaneous and is not 
completed in the furnace, as flames commonly extend over 



64 S TEA M-BOILERS. 

the bridge-wall or into the combustion-chamber; meanwhile 
there is an energetic radiation from the glowing fuel and 
flame, and a rapid transfer of heat from the hot gases to the 
heating-surface of the boiler. The better the fuel and the 
higher the hypothetical temperature of the fire the less chance 
is there that the actual temperature will approach it. 

During a test on a Babcock & Wilcox boiler, at the 
Massachusetts Institute of Technology, it was found that the 
temperature immediately over the fire was about iioo°F., 
while the temperature in the chimney was 400 F. 

A test on a boiler of the locomotive type, at the Boston 
Main Drainage Station, gave for the temperature of the gases 
escaping from the boiler 439 F., while the steam in the 
boiler was about 337° F. The gases were afterwards reduced 
to 1 94 F. by passing them through a feed-water heater. 
This boiler was designed for and gave a high efficiency, and 
the results obtained may be considered to represent first-rate 
practice. 



CHAPTER III. 
CORROSION AND INCRUSTATION. 

The water supplied to a boiler for forming steam may 
corrode the iron of the boiler, or it may deposit material that 
can form a scale or incrustation; both actions may go on at 
the same time. 

Pure water, free from air and carbon dioxide, has little or 
no solvent action on iron, even though some other metal, 
such as copper, which may with the iron form the elements of 
a galvanic couple, be present. On the other hand, iron will 
not rust if placed in an atmosphere of dry air or dry carbon 
dioxide. All natural water, rain-water, water from wells, rivers, 
lakes, or the sea, contains air in solution, and carbon dioxide 
is not infrequently found in such waters. Iron is rapidly 
acted upon by water containing air or carbon dioxide, and, on 
the other hand, iron rusts rapidly in air or carbon dioxide when 
moisture is present. Again, distilled water, as from the sur- 
face condenser of a marine engine containing more or less oil, 
or the substances resulting from the action of steam on oil, 
causes corrosion in boilers that are free from scale. To avoid 
rusting of boilers when not in use they ought to be either 
quite dry inside or they ought to be entirely filled with 
water — preferably water that has been freed from air by boil- 
ing. In the American Navy it has been the custom to dry 
out boilers and paint them inside with mineral oil preparatory 
to laying them up. In the English Navy the boilers are 
dried out, a pan of glowing charcoal is placed in the boiler to 

65 



66 



S TEA M-B OILERS. 



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CORROSION AND INCRUSTATION. 6? 

consume the oxygen of the air, and quicklime is introduced 
to absorb moisture. 

Mineral Impurities. — The impurities found in water sup- 
plied to land boilers are commonly carbonate of lime and 
sulphate of lime, with more or less organic matter, and some- 
times sand or clay held in suspension. The table on page 66 
gives the number of grains of various mineral substances held 
in solution in water from several sources. 

Water supplied to land boilers is either hard or soft ; the 
first contains appreciable quantities of lime, and the other 
usually contains little solid matter of any sort. The first three 
examples in the table on the preceding page may be taken as 
typical soft waters, and all the others, except the last two, as 
typical hard waters. While there is considerable difference 
in the amounts and the composition of the solids in solution 
in the several examples of hard water, it will be seen that 
they are all characterized by a considerable amount of calcium 
and magnesium carbonates, and (with the exception of Nos. 6 
and g) accompanied by a comparatively small amount of cal- 
cium and magnesium sulphates. It will be noticed that Mis- 
souri River water is distinctly worse than Mississippi River 
water, not only in that it contains more of the carbonates, 
but because it contains a considerable quantity of sulphates. 
No. 9, from a well at Downer's Grove on the C, B. and Q. 
R. R., a few miles from Chicago, has been selected as an 
example of a very bad hard water, especially as it contains so 
much sulphate. The reason for considering the sulphates of 
lime and magnesia so deleterious will appear a little later. 
Note will be made that the water from the Mississippi River 
at two different places, and presumably at different seasons of 
the year, vary considerably, especially in the amount of mat- 
ter held in suspension. 

In some places in the western parts of the United States 
the only available waters for making steam are strongly im- 
pregnated with alkalies and borax. Such waters havj sc 



68 STEAM-BOILERS. 

deleterious an action on boilers that the advisability of using- 
a surface condenser, as at sea, the distillation of water by a 
multiple-effect evaporator, or the introduction of a supply of 
good water even from remote places, is worthy of considera- 
tion. If the use of such water cannot be avoided, a competent 
chemist should be consulted to suggest methods for ameliorat- 
ing the bad effects so far as possible. As each case is liable 
to require special treatment, no further discussion appear 
profitable in this place. 

The carbonates of lime and magnesia are held in solution. 
in water by an excess of carbon dioxide and are completely 
precipitated by boiling. They are thrown down from water 
supplied to a boiler, in the form of a white or grayish mud, 
provided there are not other impurities that cement them to 
gether and form a hard scale. The customary and sufficient 
method of treating boilers supplied with water containing car- 
bonates of lime and magnesia is to let the boiler, while full, 
cool down, and then run out the water and thoroughly wash 
out the boiler with a strong stream from a hose. If the water 
is blown out under steam-pressure the deposits are hardened 
and are removed with difficulty. While pure carbonates are 
easily treated as just described, the presence of other impu- 
rities, such as oil or organic matter, or of sulphate of lime, is 
likely to make the deposits hard and adhering. 

Sulphate of lime is much more soluble in cold than in hot 
water, and is entirely thrown down from water at a tempera- 
ture of 280 F., corresponding to 35 pounds pressure of steam 
above the atmosphere. It forms a hard and adhering scale, 
and even in comparatively small quantities has a bad effect on 
scales and deposits composed of carbonates, as has already 
been suggested. The bad effect of deposits from water con- 
taining calcium sulphate is much ameliorated by introducing 
carbonate of soda or soda-ash into the boiler with the feed- 
water. The result is to give a deposit of calcium carbonate 
in the form of a fine white powder, which must be washed 



CORROSION AND INCRUSTATION. 69 

or swept out, and sodium sulphate in solution, which must be 
blown out from time to time. 

If the mineral matters in the water are known from a 
chemical analysis, the quantity of carbonate of soda to be used 
may be calculated as follows: 

Example. — Find the weight of carbonate of soda required 
per day for a boiler supplied with 1000 gallons of water per 
day from the well at Downer's Grove. 

From the table on page 66 it appears that each gallon of 
the water contains 14.037 grains of CaS0 4 and 25.422 grains 
of MgS0 4 . The formula for soda crystals being Na 2 C0 3 + 
ioH 2 0, the reactions, neglecting the water of crystallization, 
will be 

CaS0 4 + Na 2 C0 3 = CaCO s + Na a S0 4 ; 
MgS0 4 + Na,CO, = MgCO, + Na 2 S0 4 . 

If x x is the grains of carbonate of soda to act on the cal- 
cium, we have 

CaS0 4 ;Na 2 C0 3 + ioH 2 = 14.037 \ x x \ 
40 -j- 32 + 4 X 16 : 2 X 23 + 12 + 3 X 16 + 10(2 -f 16) 

= 14.037:*,. 
.*. x t = 29.52 grains. 

The magnesium sulphate which is soluble is also changed 
into the carbonate and thrown down as a white precipitate, 
adding to the deposit. The number of grains of carbonate 
■of soda required for this reaction is found as follows : 

MgS0 4 :Na 2 C0 3 + ioH 2 = 25.422:*,; 

24+ 32 +4 X 16:2 X 23 + 12 + 3 X 16+ 10(2+16) 
= 25.422 : * 2 . 
.-. x 2 — 60.59 grains. 

The total weight of carbonate of soda per gallon is therefore 
29.52 + 60.59= 90+, 



70 S TEA M-B OIL ERS. 

and the weight required for iooo gallons is 

qo X iooo . . 

. = 12.9 pounds per day. 

7000 

It is advisable that soda, or any other chemical for acting 
on the impurities of feed-water, shall be introduced at regular 
intervals. Sometimes a weight, or measured portion, is thrown 
into the feed-water in a tank or reservoir, from which it is 
pumped. Sometimes the chemical, dissolved in water or 
diluted with water, is placed in a small tank or receptacle that 
may be temporarily connected with the suction of the feed- 
pump. If this method is used care must be taken not to 
admit air to the pump and so derange its action. 

Soda-ash is commonly used instead of carbonate of soda, 
as it is cheaper and somewhat more efficient, on account of the 
caustic soda it may contain. Its chemical composition is 
uncertain, and it is therefore impossible to make satisfactory 
calculations for the quantity to be used. This, however, is 
commonly no real objection, for we seldom have a chemical 
analysis of the water, and cannot determine directly how much 
soda is required. 

An excess of soda in a boiler is liable to cause foaming, 
and at high temperatures, corresponding to pressures now ha- 
bitual for steam-boilers, the soda is apt to attack the inside of 
water-glasses ; any indication of either action should raise the 
question whether too much soda is used, but the absence of 
such an indication does not show that we are using the right 
quantity. When a hard scale is formed by a water known to 
contain lime, we may infer that sulphates are present, and may 
find by trial the amount of soda to be used. Unfortunately 
other impurities, such as organic matter, cause the formation 
of hard scale, and make this method uncertain. Such impur- 
ities often produce discoloration, and thus betray their pres- 
ence. The deposits of lime, whether carbonates or sulphates,, 
are commonly white or grayish, or sometimes fawn color. 



CORROSION AND INCRUSTATION. 7 1 

It is sometimes proposed to use ammonium chloride, or 
sal-ammoniac, to break up lime compounds ; in the first 
place, only the carbonates are acted upon by this reagent, 
and in the second place, the reagent itself, or the resultant 
chlorides, are liable to be broken up, giving free chlorine, 
which attacks the boiler. 

Tannic acid, either commercial acid or in the crude state, 
may be used to break up a scale already formed ; but as 
tannic acid does not decompose the sulphates , and as the 
compound of the acid with lime is not soluble, its use appears 
to be restricted. Many proprietary boiler compounds depend 
on tannic acid for their action. Acetic acid may also be 
used to break up the carbonates, but it likewise has no action 
on the sulphates ; the carbonates are changed into soluble 
acetates, and can be blown out. Both tannic acid and acetic 
acid attack iron, but are not so dangerous as sulphuric or 
hydrochloric acids, which are sometimes recommended for 
breaking up scale. When a scale is once formed the safer 
way is to remove it with proper chipping and scaling tools ; 
but this will be found to be impossible for many types of 
boilers unless they are largely dismembered for that purpose. 

When river-water is used in boilers, various earthy im- 
purities are liable to be carried into boilers, such as'clay and 
sand, together with soluble matters. Even waters from 
ponds or wells may contain considerable matter in suspension. 
Such substances can sometimes be removed by filtering or by 
allowing the water to stand so that the insoluble matter may 
be deposited. Very commonly a systematic blowing out 
from the surface of the water and the bottom of the boiler 
will remove such impurities from the boiler. If, however, 
lime and magnesium carbonates and sulphates are present, 
suspended matter is carried into the scale, and the scale may 
be made more troublesome in consequence. The carbonates 
are more likely to form a hard scale if any binding material, 
such as clay, is present. 



72 



S TEA M-B OILERS. 



Fig. 28 shows the section of a feed-pipe which was nearly 
choked with scale from lime-water. Though the deposit of 
scale in a horizontal piece of feed-pipe where the water may 
be heated by conduction and otherwise, especially during 
intervals of feeding, is probably more rapid than in the boiler 
itself, this may serve to call attention to the extent to which 
scaling may occur when precautions are not taken. 




Fig. 28.* 

Lime-extracting Feed-water Heater. — It has been 
pointed out that carbonate of lime can be completely pre- 
cipitated by boiling to drive off the excess of carbonic acid ; 
carbonate of magnesia if present is thrown down at the same 
time. Also sulphate of lime is thrown down at 280 F., cor- 
responding to 35 pounds pressure above the atmosphere. 
It is evident that lime compounds can be removed from feed- 
water by heating it and removing the precipitated lime before 
feeding it to the boiler. For this purpose we may use a 
heater such as the Hoppes heater and purifier shown by Fig. 
29, which consists essentially of a series of cylindrical pans 



* This figure and Figs. 31 to 35 were kindly loaned by the Hartford Ste^m 
Boiler Inspection and Insurance Co. 



CORROSION AND INCRUSTATION 



73 



of sheet steel, I, 2, 3, 4, 5, and 6. The feed-water is pumped 
into the upper pan, from which it overflows, and, trickling 
along the bottom, it drops into the pan 2. From 2 the 
water overflows into 3, and so on. 

The capacity of the heater depends on the number of 
sets of pans, which varies from one to four. The pans are 
enclosed in a steel shell, from which one end may be removed 
for cleaning the pans. Feed-water is pumped in at B ; steam 
from the boiler is admitted at A ; the feed-water after being 
heated and purified runs out at D on the way to the boiler; 




Fig. 29. 

at C there is a blow-out, from which air and gases may be 
blown out when the heater is started, or at other times. 

It is desirable that the pipe D shall drop down below the 
water-level in the boiler before any turns or horizontal pipes 
are attached. The water runs from the heater to the boiler 
by gravity only, and the heater must be placed high enough 
for this purpose. It is also desirable that the feed-pump be 
supplied with steam from the heater so as to continually 
remove the carbonic acid, air, or other gases given off from 
the feed-water. 



74 



6" TEA M-BOILERS. 



The feed-water as it trickles along the under sides of the 
pans in a thin film is heated by the steam, and the lime com- 
pounds are deposited in form of a scale or incrustation, 
Meanwhile mud, sand, and other mechanical impurities settle 
to the bottom of the pans. 

After the heater has been at work a month or so, depend- 
ing on the amount of lime in the water, the pans must be 
removed and cleaned. The steam-pipe and the pipe leading 
to the boiler are shut off by proper valves, and cold water is 
pumped in and allowed to run to waste at the blow-off. The 
contraction of the pans cracks off hard scale and makes it 
easier to remove. When the heater is first opened the scale 
is usually soft and can be readily removed; it is liable to 
harden when exposed to the air and allowed to dry. 

A heater for use with exhaust-steam, by the same makers, 
differs from this mainly in that there is a device for extract- 
ing oil from the steam before it meets the feed-water, and in 
that it is run at atmospheric pressure. Such a heater will not 
remove sulphate of lime ; and further, since it is difficult if 
not impossible to remove oil from exhaust-steam, it is proba- 
ble that some oil will be carried over into the boiler. 

Sea-water. — The following table gives an analysis of sea- 
water by Professor Lewes of the Royal Naval College, to- 
gether with an analysis by him of a typical boiler deposit from 
a marine boiler: 

SALTS IN SEA-WATER AND COMPOSITION OF MARINE- 
BOILER SCALE.* 



Calcium carbonate (chalk). . 
Calcium sulphate (gypsum). 

Magnesium sulphate 

Magnesium chloride 

Magnesium hydrate 

Sodium chloride (salt). . . . 

Silicia (sandy matter) 

Moisture 



Sea-water. 


Marine-boiler 


Grains per Im- 


Scale. 


perial Gallon. 


Per Cent. 


3-9 


O.97 


93-1 


85.53 


124.8 




220.5 






3-39 


1 8 50. 1 


2.79 


8.4 


I.I 




5-9 



Trans. Inst. Naval Arch., vol. xxx. p. 330. 



CORROSION AND INCRUSTATION. y$ 

The three principal constituents of the marine scale are cal- 
cium sulphate, calcium carbonate, and magnesium hydrate, 
of which the first forms the greater part of the scale. 

The calcium carbonate is kept in solution by the carbonic 
acid in the sea- water, just as is the case for fresh water con- 
taining carbonate of lime, and is deposited when the carbonic 
acid is driven off by heat. There is, however, a reaction 
between the calcium carbonate and magnesium chloride at the 
temperature and pressure in the boiler, giving a deposit of 
magnesium hydrate and leaving calcium chloride in solution, 
so that only part of the calcium carbonate appears in the scale ; 
and on the other hand, we may thus account for the presence 
of the magnesium hydrate in the scale. 

The calcium sulphate forms so large a part of the scale, that 
we will give attention to it only in the further discussion. Cal- 
cium sulphate is more soluble in water at 95 ° F. than at any 
temperature higher or lower; and the solubility decreases with 
the rise of temperature, till at about 280 F., which corre- 
sponds to 50 pounds pressure absolute to the square inch, or 
35 pounds above the atmosphere, the entire amount of cal- 
cium sulphate is deposited. In the early history of the marine 
engine, when low pressures of steam prevailed, we find jet con- 
densers in use, and the boilers, which were fed from the brine 
in the hot-well, were kept fairly free from scale by blowing 
out the concentrated brine. It was then customary to supply 
half again as much feed-water as was evaporated, the excess 
being compensated by the concentrated brine blown out, and 
the water in the boiler had three times the degree of concen- 
tration found in the sea. As high-pressure steam came into 
use, surface condensers became indispensable. When surface 
condensers first came into use the waste of steam from leakage 
and otherwise was made up from water taken from the sea, 
with the result that the boilers gradually accumulated a heavy, 
dense scale. Since it is customary to have an auxiliary boiler, 
called a donkey-boiler, on steamships, the first device to avoid 
the scaling from the use of sea-water in the main boilers appears 



j6 S TEA M-B OILERS. 

to have been to supply the loss of steam from the donkey- 
boiler, which was fed from the sea. This of course only trans- 
ferred the difficulty from one place to another, even though a 
less objectionable one. At present the loss is made up by 
vaporizing sea-water in a special boiler, which is heated by 
steam-coils supplied with steam from the main boilers. The 
pressure may be low enough in this vaporizer to avoid the 
total precipitation of the calcium sulphate, and the brine may 
be kept at any desirable degree of saturation by blowing out, 
as in the early marine practice ; and further, the vaporizer is 
so made that the steam-coils may be readily cleared from 
scale. 

It should be pointed out that the decomposition of the 
calcium sulphate in sea-water by the aid of soda is impracti- 
cable, on account of the large quantity of magnesium carbonate 
thrown down by reaction on the magnesium sulphate. 

A boiler fed with water condensed in a surface condenser, 
as is now common in marine practice, is liable to two diffi- 
culties : (i) the distilled water is apt to corrode or pit the plates 
of the boiler, and (2) the cylinder-oil used in the engine is 
liable to be carried over into the boiler and form oily scales 
and deposits. 

When sea-water is used in the boiler, either as the main 
boiler-feed or merely to supply the waste, the boiler-plates are 
protected by the scale of calcium sulphate, and general corro- 
sion or local pitting is seldom troublesome. When care is 
taken to avoid the use of salt water, supplying the waste with 
fresh water from a distiller or otherwise, general corrosion and 
local pitting have both been found to occur to a dangerous 
degree. A simple remedy appears to be to form a very thin 
scale by the use of sea-water, and then avoid further use of 
sea-water. It is, however, found that water from a surface 
condenser will gradually dissolve off such a scale, and it must 
be occasionally renewed. There is also an objection to tne 
introduction of any lime compound into a boiler, as wili appear 



CORROSION AND INCRUSTATION. 7 J 

in the discussion of the difficulty from the collection of oil in the 
boiler. In both the United States and the English navies it is 
customary to use slabs of zinc to protect the boiler-plates from 
corrosion. The zinc is fastened to or hung from the boiler- 
stays, with which metallic connection should be made to in- 
sure galvanic action. The zinc is gradually consumed, and 
becomes soft and friable, so that the slabs require renewal. 
It is recommended to supply 1/4 of a pound of zinc for each 
square foot of grate-surface. 

It is a familiar fact that the cylinders of an engine may be 
oiled by introducing the oil into the supply-pipe, and that the 
oil will be carried quite thoroughly over the surface of the 
cylinder by the steam; and, further, that the oil is carried out 
of the cylinder by the steam, and will appear in the condensed 
water in the hot-well. It is evident that any oil is liable to 
be injurious if it gets into a boiler. It is, consequently, cus- 
tomary to filter the water from a surface-condenser, to remove 
the oil as far as possible. For this purpose sponges have 
been used in the navy ; they, of course, must be occasionally 
taken out and washed free from oil. A very simple and effi- 
cient filter has been made in the form of a rectangular box, 
with perforated plates near the ends; the water from the hot- 
well runs into one end compartment, passes through a mass of 
hay in the middle compartment, and is drawn from the further 
end compartment by the feed-pump. When the hay becomes 
foul it is thrown away, and fresh hay is put in. Professor 
Lewes advises for a filter a long tube filled with charcoal 
about the size of a walnut; of course the charcoal should be 
renewed when necessary. It cannot be expected that any 
system of filtering will remove all the oil from the water, but 
the larger part may be removed. It is advisable that no more 
oil than necessary shall be used in the cylinders of the engine. 

Professor Lewes" gives the following account of an inves- 

* Trans. Inst. Nav. Arch., xxxu. page 67. 



7 8 STEAM-BOILERS. 

ligation of the collapse of the furnace-flues of a large Atlantic 
steamer, which made the voyage in twelve days : 

The boilers were five and a half years old, and were refilled 
with fresh water at the end of each voyage, while the waste of 
the voyage was made up by the use of about yo tons of fresh 
water, but during the last voyage sea-water was used for this 
purpose. Every four hours, while under steam, four pounds 
of soda crystals were put in the hot-well, making two hundred- 
weight during the run, the total capacity of the boilers being 
8 1 tons. ' For lubricating purposes seven pints of valvoline 
were used in the cylinders every four hours. 

When in port the boilers were allowed to cool down, and 
the water was run off and they were swept down with stiff 
brushes, and were afterwards sluiced out with a hose shortly 
before being filled with fresh water. No trouble occurred 
until five voyages before the final collapse, when some of the 
furnaces began to creep in : they were stiffened with rings and 
stays; and on succeeding voyages the whole of the furnaces 
got out of shape one after the other. Examination showed 
that they had never been very heavily scaled. On the furnace- 
crown there was only a slight white scale not more than 1/64 
of an inch thick, while on the bottom of the furnaces there was 
a brown oily deposit 1/16 of an inch thick, which in other 
parts of the boiler increased to 1/8 or 3/16 of an inch. 

The valvoline was a pure mineral oil with a specific gravity 
of 0.889 and a boiling-point of 371 C. 

The composition of scales from several parts of the boiler 
is shown in the table on the next page. 

Careful examination of the organic matter and oil in these 
deposits showed that half of it was valvoline in an unchanged 
condition, which had collected around small particles of calcic 
sulphate. 

All the deposits were rich in oily matter except the top 
of the furnaces, i.e., the place where the collapse occurred. 
There the scale was not only nearly free from oil, but per- 
Meetly harmless both in quantity and quality. It appeared 



CORROSION AND INCRUSTATION. 
COMPOSITION OF DEPOSITS IN A MARINE BOILER. 



79 



Calcium sulphate 

Calcium carbonate 

Magnesium hydrate 

Iron, alumina, siiica 

Organic matter and oil . . 

Moisture 

Alkalies 





S u" 


u 


V 




c u 







a v 
o y 


3 ~ 


h 


•° s 


Hg 


e a 


c 


- u w 


e 3 


B fa 





C -3 


Ofc 


c -n 


a 


uc/)H 


fa 


i. 


in 


P 


84-87 


59-n 


50.92 


II.60 


5.90 


6.07 


4.18 


O.S2 


2.83 


11.29 


14.12 


22.21 


2-37 


2.85 


7-47 


9.I4 


3-23 


19-54 


21.06 


50.20 


0.S0 


1.14 


1. 17 


4 23 






1.08 


1. So 



o o 
Q 



entirely improbable that the scale on the top of the furnaces 
could be in its original condition. 

When oil has entered a boiler the minute globules, if in 
large quantity, coalesce to form an oily scum on the surface, 
or if in small quantity remain in separate drops, but show no 
tendency to sink on account of their low specific gravity. 
They, however, come in contact with solid particles of calcium 
sulphate, coat them with oil, and so the light oil becomes 
loaded till it is easily carried along by convection-currents and 
adheres to surfaces with which it comes in contact, which 
are quite as likely to be the under surfaces of tubes as the 
upper surfaces. Since some brine is liable to find its way to 
the boiler, from leakage into the condenser or otherwise, even 
when sea-water is not used directly, this action will occur in 
a boiler supposed to contain fresh water only. 

The deposits thus formed are very poor conductors of heat, 
and the oily surface interferes with contact with water. On 
the crown of the furnace this soon leads to overheating of the 
plates, and the deposit begins to decompose, the lower layer 
in contact with the plate giving off gases which blow up the 
greasy layer, ordinarily only 1/64 of an inch thick, to a spongy 
mass 1/8 of an inch thick, which, because of its porosity, is even 
a better non-conductor of heat than before, and the plate be- 
comes heated to redness and collapses. During the last stages 



80 STEAM-BOILERS. 

of this overheating the temperature has risen to such a point 
that the organic matter, oil, etc., in the deposit burns away, 
oris distilled off, leaving behind, as an apparently harmless 
deposit, the solid particles round which it had originally formed. 

Such a deposit is more likely to be produced in boilers 
containing fresh or distilled water, as the low density of the 
liquid enables the oily matter to settle more quickly, while 
with a strongly saline solution it is very doubtful if this sink- 
ing-point would ever be reached; it is evident also that when 
oil has found its way into the boiler and is causing a greasy 
scum on the surface the most fatal thing that can be done is 
to blow off the boilers without first using the scum-cocks, be- 
cause as the water sinks the scum clings to the tops of the fur- 
naces and other surfaces with which it comes in contact, and 
on again filling up with fresh water it still remains there, 
causing rapid collapse. A very remarkable instance of this 
is to be found in the case of a large vessel in the Eastern trade, 
in the boiler of which an oil-scum had formed. The ship 
having to stop some days in Gibraltar, the engineer took the 
opportunity of blowing out his boiler and refilling with fresh 
water, with the result that before he had been ten hours under 
steam the whole of the furnaces had collapsed. Under some 
conditions the oil-coated particles coalesce and form a sort of 
floating pancake, which, sinking, forms a patch on the crown 
of the furnace at one particular spot, and under these condi- 
tions the general result is the formation of a pocket. 

A curious fact is that these oily deposits are found to con- 
tain a considerable amount of copper. Even mineral oils have 
a solvent action on copper and its alloys, and it is evident 
that the copper in the oily deposits has been obtained from 
the fittings of the cylinder and condenser. Fortunately this 
copper is protected by oil, otherwise serious galvanic mischief 
would result. 

Professor Lewes found from experiment that a coating, 1/16 
of an inch thick, of the oily deposit found in the bottom of a 



CORROSION AND INCRUSTATION. 8 1 

boiler, applied to the inside of a clean iron vessel, very greatly 
retarded the transmission of heat from a Bunsen flame, as 
shown by the time required to heat a known quantity of water 
to boiling-point. Using an atmospheric blowpipe, he succeeded 
in raising the outside surface of the vessel, when coated with 
1/16 of an inch of the deposit, to the temperature of the melt- 
ing-point of zinc, and with an oxy-coal-gas flame he fused a 
hole in the bottom of a thin wrought-iron vessel thus coated 
and filled with water. 

He further says that cylinders should be sparingly lubri- 
cated with a pure mineral oil having a high boiling-point, and 
that animal or vegetable oil should never be used, because 
they are decomposed by the action of high-pressure steam, 
producing fatty acids that attack iron, copper, and copper 
alloys. 

Professor Lewes has proposed that marine boilers at sea 
shall have the water supplied with brine from which the lime 
compounds have been precipitated in a closed receptacle by the 
combined action of heat and carbonote of soda. The resulting 
brine contains mainly sodium and magnesium chlorides and 
magnesium sulphate, which do not form scale even though the 
concentration is carried to a higher degree than would occur 
from the supply of the waste of the boiler in this way for a 
voyage of some length. This method has not as yet been 
adopted in practice. Attention is called to the fact that an 
excess of soda should be avoided, since it would cause a bulky 
deposit from the action on the magnesium sulphate brought in 
by leakage of sea-water into the condenser. A description of 
the apparatus for producing this brine without lime salts is 
given in the "Transactions of the Institution of Naval Archi- 
tects" (see the leference, page 74). 

Organic Impurities. — Water for feeding boilers, unless 
taken from a contaminated source, seldom contains much 
organic matter. Surface water from rivers or ponds may con- 
tain some vegetable matter, but if there are no other impun- 



82 



S TEA M-B OILERS. 



ties such organic matter will not cause much trouble unless it 
is allowed to accumulate. The vegetable and other organic 
impurities commonly float on the surface of the water when 
the boiler is making steam, or are carried around by convec- 
tion-currents, and may be blown out through a surface blow- 
out, shown by Fig. 30. It consists essentially of a flattened 




Fig. 30. 

bell or cone of sheet metal extending across the boiler at the 
water-level, and turned so that the convection-currents will 
carry and lodge floating substances in the mouth of the bell. 
The valve in the pipe leading from this bell may be opened 
from time to time to blow out the substances collected in it. 

When a boiler has been at rest for some time, overnight 
for example, the various solids in the boiler, if heavy enough, 
will settle to the bottom, and may be advantageously blown 
out before starting the boiler into action again. This may be 
accomplished by opening the blow-out valve or cock for a short 
time, until the water-level falls a few inches. 

Water from bogs frequently contains vegetable acids that 
are likely to corrode the plates of the boiler: in such cases 



CORROSIOX AND INCRUSTATION. 



83 



carbonate of soda may be used to neutralize the acids; the 
proper amount must be found by trial. 

The oil used in the engine is liable to get into the ooiier 
if surface-condensing is made use of; this subject has already 
received attention in connection with the discussion of marine- 
boiler incrustations. Surface condensers are not commonly 
used in land practice, but very commonly the exhaust-steam 
from non-condensing engines 
is used for heating in radiat- 
ing-coils, and there is an ap- 
parent gain from the use of 
the warm water from the 
return-pipes. This water is, 
however, liable to be con- 
taminated by oil, and the 
oil when it gets into the 
boiler may cause serious 
damage, such as was found 
to occur in marine boilers. 
If the feed-water has a little 
vegetable matter in it, the 
effect of the oil is much worse 
than if the water-supply is 
pure. Again, the oil is very 
troublesome if the water con- 
tains lime salts. The bad 
effect of oil or other impur- 
ities on lime-scale has been 
already noted. Usually it 
will be found better to reject 
the water returned from a 
heating system supplied with 
exnaust-steam, as the ap- 
parent economy is liable to 
be more than counterbalanced by damage to the boiler. The 




84 S TEA M-B OILERS. 

externally-fired tubular boilers commonly used in this part of 
the country are liable to bulge in the sheets over the furnace, 
as shown in Fig. 31, if oil gets into them. When the plate 
is cut out a hard deposit of oil, commonly mixed with other 
impurities, will be found adhering to the plate ; this deposit 
is a very poor conductor of heat, and it causes so much over- 
heating of the plate that it bulges out under the pressure of 
the steam. 

In isolated cases it will be found that water of a stream 
may be so contaminated with chemicals from some industrial 
establishment that it acts energetically on the boiler-plates; 
in such case the water must be abandoned unless the contam- 
ination can be stopped. 

Kerosene and Petroleum Oils. — Both crude petroleum 
and refined kerosene have been used in steam-boilers to miti- 
gate the effect of incrustations of calcium carbonate and calcium 
sulphate. From what is known of the bad effects of the 
heavier petroleum products, such as the mineral oils used for 
lubricating steam-engine cylinders, it appears to be unwise 
to introduce crude petroleum into a steam-boiler. The same 
objection does not apply to refined kerosene, which is not 
known to have any bad effect in a boiler. Both oils are said 
to change the deposits of lime from a hard scale to a friable 
material, which may be easily removed. It is further said that 
these oils will soften and loosen scale already formed. In one 
case 40 gallons of kerosene were used in 24 hours in the 
boilers of a steamer of about 3000 horse-power. These 
boilers showed no incrustation, but considerable corrosion. 

Corrosion is distinguished as general corrosion or wasting, 
pitting, and grooving. 

General corrosion is difficult to detect, as it acts more or 
less uniformly over large surfaces, and even at riveted joints 
the two plates and the rivet-heads waste away equally, so that 
the thinning of the plates is not easily noticed. Old boilers 
not infrequently fail from general corrosion, and then are 



COA'ROSION AND INCRUSTATION. 



85 



likely to fail in the plate rather than in the riveted joint, where 
the double thickness of plate gives an advantage. Boilers 
that have been at work should have the plates below the water- 
line drilled and the thickness measured; if the effective thick- 
ness of the plate is found to be much reduced, the working 
pressure should be made proportionately lower. Fig. 32 




shows an example of general corrosion, and Fig. 33 another, 
but complicated with cracking at the rivet -holes. Both show 
the protection given to the plate by the rivet-heads, and one 
may readily see how the wasting of the rivet-heads may be 
overlooked. 

Pitting is likely to occur when the corrosion takes place 
rapidly. It appears to be due to lack of homogeneity of 
the metal of the plate, and sometimes appears to indicate 
galvanic action. Though every precaution to avoid gal- 
vanic action should be taken, it is better to assume damage 
to be due to such action only when there is direct evi- 
dence of its existence. Fig. 34 shows pitting over a large 
surface, and Fig. 35 shows local pitting in the corner of a 
flanged plate with general corrosion of the flat surface of the 
plate. It is fair to assume that the disturbance of the metal 
in the process of flanging may determine the vertical forms 
of the pitting. The horizontal plate shows irregular pitting. 

Grooving is usually due to the combination of springing 
or buckling of a plate and local corrosion. The buckling may 
be due to insufficient staying; then the plate springs back 
and forth as the steam-pressure varies. Or buckling may be 
due to improper staying or fastenings, which localizes the 



86 



6 1 TEA M- BOILERS. 











II 



Fig. 35- 



CORROSION AND INCRUSTATION. 87 

change of shape due to expansion. In either case the metal 
is fretted at the place where the greatest bending takes place, 
and very much weakened. A crack is liable to be formed, 
which may grow wider and deeper till the plate shows signs 
of failure. Such cracks may be very narrow and difficult to 
find, but usually the fretting of the metal, whether a crack is 
formed or not, is accompanied by local corrosion, which 
makes a groove of some width. If the water used forms a 
scale on the boiler-plates, the working of the metal throws 
off the scale and exposes the surface to the water so that cor- 
rosion takes place there, though elsewhere the plate is pro- 
tected. 

As one example of insufficient staying, we may take the 
flattened surface in a wagon-top locomotive-boiler (Plate II), 
where the barrel is expanded to join the shell over the fire- 
box. The surface cannot be stayed from side to side for lack 
of space between the tubes, and is merely stiffened by rivet- 
ing three .pieces of T iron to the shell. In this case the T 
irons have through-stays at their upper ends over the tubes. 
Grooving is liable to occur in this locality even when the 
plates are stiffened as shown. 

Grooving from too great rigidity is liable to occur in the 
end-plates of Cornish and Lancashire boilers (see pages 6 and 
7). The long furnace-flues expand more than the external 
shell, and expand more at the top than at the bottom, due to 
the heat of the furnace and of the gases in the flue beyond 
the furnace ; and further, the circulation of water under the 
flues is likely to be imperfect, so that the bottom of the flue 
is not so hot as the top. These unequal expansions must be 
accommodated by the springing of the end-plates, and if the 
springing is too much localized, grooving is sure to occur. 
The furnace-flues should be at least nine inches from the 
shell, and the end-plates should be flanged where they are 
joined to the flues and shell, instead of using angle-irons. 
The use of gusset-plates for staying the ends of these boilers 



88 S TEA M-B OILERS. 

is likely to give too much rigidity and to localize the spring- 
ing of the plates, unless care is taken to avoid it. 

Grooving from either too great or too little rigidity can be 
avoided only by a proper design, which must be guided by 
experience. If a boiler shows defects of staying, it may be 
possible to put in additional stays after the boiler is com- 
pleted and at work; or in some cases too great rigidity may 
be remedied by rearranging the staying. Such remodelling 
of a boiler is usually difficult and unsatisfactory. 

Loss from Blowing Out Brine. — In the discussion of 
the use of sea-water in marine boilers, reference was made to 
the custom of feeding one-and-a-half times as much water as 
was evaporated. The feed-water was taken from the hot- 
well of the jet condenser, and was nearly as salt as sea- water, 
which contains about 1/32 of its weight of salt. The one- 
half excess of water fed was blown out, and carried with it all 
the salt of the entire feed-water; it consequently contained 
3/32 of its weight of salt, and the brine in the boiler had the 
same degree of concentration. 

In calculating the loss from blowing out hot brine it is 
customary to assume that the specific heat of sea-water and 
also of the hot brine is the same as that of fresh water; accu- 
racy in this calculation is not essential. 

For example, find the loss from blowing out hot brine to 
maintain the concentration in the boiler at 3/32, when the 
boiler-pressure is 30 pounds by the gauge and the temperature 
in the hot- well is 140 F. 

The absolute pressure corresponding to 30 pounds by the 
gauge is 44. 7, found by adding the pressure of the atmosphere. 
Since no refinement is needed in this calculation we will use 
instead 45 pounds absolute. A table of the properties of satu- 
rated steam (see Appendix) gives for the heat of the liquid at 
45 pounds absolute, 243.6 thermal units; this is the heat re- 
quired to raise one pound of water from 32 F. to 274°.3 F. v 
that is, to the temperature of steam at the pressure of 45 



CORROSION AND INCRUSTATION. 89 

pounds. The same tabic gives for the heat required to vapor- 
ize one pound of steam from water at 274 .3 against a pres- 
sure of 45 pounds, 922 thermal units. But it is assumed that 
the feed-water has a temperature of 140 F. when taken from 
the hot-well; the corresponding heat of the liquid is 108.2 
thermal units. Consequently, to raise a pound of water from 
140 F. and vaporize it under the pressure of 45 pounds will 
require 

922 -\- 243.6 — 108.2 = 1057.4 

thermal units. This is the heat usefully employed. 

Meanwhile for each pound of water vaporized half a pound 
of water is heated from 140 F. to 274°.3 F., and then thrown 
away. The heat required to raise half a pound of water from 
140 F. to 274°.3 F. is 

4(243.6— 108.2) = 67.7 

thermal units. This is the heat wasted. 

The total heat applied to forming steam and heating the 
brine blown out is 

1057.4+67.7= 1125.1. 
The per cent of heat wasted is consequently 

67.7 
100 X — — L - = 6 per cent. 
1 125. 1 

A considerable portion of the heat lost in the hot brine 
may be transferred to the feed-water drawn from the hot-well 
by the aid of a feed-water heater, and thus saved. A simple 
form of heater may be made by carrying the hot brine 
through a small pipe inside the feed-pipe ; the currents of 
water will naturally flow in opposite directions, and thus give 
the most efficient interchange of heat. If the hot-well is near 
the boiler, the feed-pipe may not be long enough to allow of 
this form of heater. 



90 STEAM-BOILERS. 

The density of brine in the boiler is ascertained by a 
salimeter, which is a form of hydrometer graduated to read 
zero in fresh water, 1/32 in sea- water, and the graduation is 
extended to give the density of brine in thirty seconds, so far 
as may be needed. When jet condensers were used at sea it 
was customary to carry the density to 3/32 only. With sur- 
face condensers the density is frequently carried as high as 
6/32 ; no inconvenience is found in this custom, and as less 
water is taken from the sea the formation of incrustation is 
less rapid. 



CHAPTER IV. 
SETTINGS, FURNACES, AND CHIMNEYS. 

The Boiler-setting for a stationary boiler consists of the 
foundation and so much of the flues and furnace as are ex- 
ternal to the boiler proper. The entire furnace of externally- 
fired boilers is in the setting, and in some cases, as with the 
plain cylindrical boiler, the flues are also formed by the set- 
ting. Some internally-fired boilers — for example, the Lanca- 
shire boiler — have flues in the setting in addition to the boiler- 
flues; others, like the upright boiler (Fig. 5, page 10), have 
only a foundation. Locomotive-boilers rest on the frame of 
the locomotive; they can scarcely be considered to have any 
setting. Marine boilers are seated on plates that are built 
into the framing of the ship. 

Cylindrical Tubular Boiler-setting. — The setting for a 
pair *of cylindrical tubular boilers, like the boiler represented 
on Plate I, is shown by Figs. 36 and 37. The foundation 
for the boiler-setting is a solid bed of concrete 17 feet 8 
inches wide, and 21 feet 8 inches long, and 24 inches thick. 
On firm soil the foundation may be conveniently made of 
large rough-stone work, about three feet wide, under the side, 
middle, and end walls only. 

On this foundation there are built the walls that support 
and enclose the boiler and the furnace. The outer walls at 
the sides and rear are double, with an air-space to check the 
conduction of heat. The boilers are each supported by two 
brackets at each end ; the front brackets rest on iron plates 

9 1 



9 2 



S TEA M-BOILERS. 



which are built into the side walls; the rear brackets have 
iron rollers interposed to allow for expansion. A brick 
arch is sprung over the boilers to check the radiation of heat. 
The space between the side and end walls over the boilers 
may be filled with sand, for the same purpose. Coal ashes 
are sometimes used, but they are hygroscopic and liable to 
harbor moisture when the boilers are not working, and should 



FIRE BRICK 



□ 




Fig. 36. 
not be used. Sometimes the tops of boilers are covered with 
brick and buried in sand ; or the sand may be used without 
brick. These methods give ready access to the shell for 
inspection or repairs, but are not so good as a brick arch, as 
water can more readily get to the boiler if it should drip from 
leaky valves or fittings. The rear wall is carried a little 
higher than the top row of fire-tubes, then the space is bridged 
over from the side walls by a horizontal mass of brickwork, 
stiffened and supported by T irons. The smoke-box projects 
over the front wall, and has a rectangular uptake on top, lead- 
ing to a wrought-iron flue which carries the smoke to the 
chimney. 



SETTINGS, FURNACES, AND CHIMNEYS. 



93 



The furnaces under the front ends of the boilers are 
enclosed by the side walls, the front wall, and a bridge just 

i ' ...» ff:. -u 




Fig, 37. 

beyond the first ring of the boiler-shell. The grates rest on 
the front wall and the bridge, as shown in vertical section by 



94 S TEA M-BOILERS. 

Fig. 37 and indicated in black on Fig. 36. There is a clear 
space of 24 inches between the grate and the boiler, and a 
clear space of 8 inches over the bridge. The top of the 
bridge is made of fire-brick, and all the walls of the furnaces 
and other spaces that are exposed to the fire are lined with 
fire-brick. All the remainder of the brickwork is of hard, 
well-burned brick. The ash-pit under the grate is paved with 
brick. The floor behind the bridge is covered with a layer of 
sand and paved with brick. 

The side walls are braced by three pairs of buck-staves, 
with through-rods under the paving and over the tops of the 
boilers. 

The boiler front is cast iron, with doors opening from the 
furnaces and from the ash-pits. There are also doors opening 
from the smoke-boxes to give access to the tubes. Doors 
through the rear wall give access to the space behind the 
bridge-wall. 

The setting for a two-flue boiler, or for a boiler with 
several large flues in place of the numerous fire-tubes of the 
tubular boiler, is substantially the same as those just de- 
scribed. 

Settings for Water-tube Boilers, as shown by Fig. 17, 
page 24, and Fig. 18, page 26, resemble the setting for the cylin- 
drical tubular boiler in external appearance. The furnace and 
bridge-wall are also similar to those for the cylindrical boiler. 
Special bridges, extending among and across the tubes, are 
required to give the proper circulation of the products of 
combustion. 

The Stirling boiler has a setting of special form, shown by 
Fig. 20, page 28, as required by the design of the boiler. 
The Cahall boiler has the furnace at one side of the boiler, 
which is set in a vertical brick casing or stack (Fig. 21, 
page 29). 

Water-tube boilers for marine work, like the Thornycroft 
boiler, shown by Fig. 23, page 32, and the Almy boiler, Fig. 



SETTINGS, FURNACES, AND CHIMNEYS. 95 

26, page 36, arc enclosed in a sheet-iron casing, lined with 
blocks of non-conducting material. Asbestos, or a compound 
of which magnesia is a principal ingredient, is commonly 
used. Fire-brick and pumice-stone are used with the 
Thornycroft boiler to intercept heat that would be radiated 
downward. The spaces in ships under boilers, being more or 
less inaccessible, and being subject to the influence of heat 
and moisture, are liable to show excessive corrosion. 

Furnaces. — There are certain general conditions to which 
the construction of furnaces should conform if high efficiency 
is desired. Some of these depend on the requirements for 
good combustion, and some depend on the size, strength, and 
endurance of the human frame, since hand-firing is almost 
universal. Some of these conditions are violated in the 
design and arrangement of furnaces in certain types of boilers; 
deviation from them involves either a demand for greater 
strength and skill on the part of the fireman, or a loss of effi- 
ciency, or both. 

These conditions, with examples of good and bad practice, 
are as follows : 

There should be an abundant and uniform supply of air to 
the under surface of the grate. About the only cases where 
this condition is not easily fulfilled is in the design of furnace- 
flues of Lancashire boilers and Scotch marine boilers. 

A small supply of air is required over the grate for burn- 
ing smoky fuels like bituminous coal. This air is very com- 
monly supplied through a circular grid or damper in the fire- 
door. The fire-door is commonly protected from direct radi. 
ation by a perforated wrought-iron plate, which also serves 
to distribute the air coming through this grid. Since the 
air thus supplied is cold, it must be small in amount or 
it will chill the gases and check combustion instead of 
aiding it. 

Leakage of cold air into the furnace, or into the combus- 
tion-chamber or flues beyond the furnace, injures the draught 



g6 STEAM-BOILERS. 

and reduces the temperature of the products of combustion, 
and is a direct source of loss. All externally-fired boilers and 
water-tube boilers are liable to suffer from leakage of air. 
Locomotive and Scotch marine boilers are usually free from 
this defect. 

The incandescent fuel on the grate should not come in 
contact with a cold surface. Furnaces lined with fire-brick, 
such as are used for externally-fired boilers, conform to this 
requirement. Vertical boilers, marine boilers, locomotive- 
boilers, and all other boilers having the furnaces in fire-boxes 
or flues, violate this condition, as the plates in contact with the 
fire are kept nearly at the temperature of the water in contact 
with the other side, and are therefore much colder than the 
fire. 

There should be an abundant opportunity for complete 
combustion of gases coming from the fuel with hot air drawn 
through the fuel, before the flame is chilled by contact with 
cold surfaces. This condition is best fulfilled by having a 
clear space over the grate. Externally-fired boilers commonly 
have two feet or more between the grate and the boiler-shell 
immediately over it, and combustion may continue beyond 
the bridge. Locomotive- boilers have from four to six feet 
between the grate and the fire-box crown-sheet, but the flame 
is quickly drawn into and extinguished by the tubes. To aid 
combustion and to protect the lower part of the tube-sheet a 
brick arch is frequently carried across the fire-box, over which 
the flame must pass on the way to the tubes. The lack of 
space over the grate of flue-furnaces, as in the Scotch marine 
boilers, is only partially compensated by the combustion- 
chamber beyond the furnaces. 

Loss from external radiation is almost entirely avoided in 
internally-fired boilers. Externally-fired boilers are subject 
to more or less loss from conduction and radiation. 

The fire-grate should not be longer nor wider than can be 
conveniently reached by the fireman in throwing on fuel and 



SETTINGS, FURNACES, AXD CHIMNEYS, 97 

in cleaning the grate. A narrow grate should not be so long 
as a wide grate. In general, a hand-fired grate should not be 
more than six feet long, and if it is over four feet wide two 
fire-doors should be provided. These conditions are usually 
fulfilled by the design of externally-fired boilers, locomotive- 
boilers, and water-tube boilers. Attention has been called 
already to the difficulty of getting proper space for the grates 
in flue-furnaces. With the common diameters of the furnace- 
flues a length of five feet should not be exceeded. Flues in 
marine boilers have been made eight feet long; in such case 
the further end of the grate is sure to be inefficiently fired. 
To aid in firing, and to use the space below and above the 
grate to the best advantage for the supply of air and for 
combustion, the grate is commonly given an inclination down- 
wards of about 3/4 of an inch to the foot. 

As an extreme example of deviation from these propor- 
tions we may cite the Wooten locomotive fire-box, designed 
to burn anthracite slack. The grate is made about eight feet 
wide and twelve feet long. 

For convenience in throwing on coal and in cleaning the 
grates, the floor on which the fireman stands should be about 
two feet below the grate. This can usually be arranged for 
stationary boilers. The grate of a locomotive is commonly 
below the floor of the cab ; this facilitates throwing on the 
coal ; some form of rocking grate is used to shake down the 
ashes. The side furnaces of Scotch marine boilers are com- 
monly too high for convenient firing, and the middle furnaces 
may be too low for convenience in cleaning the grate. 

Excessive heat in the fire-room should be avoided as far as 
possible ; the labor of feeding and cleaning a furnace for rapid 
combustion is always severe, and when combined with great 
heat it soon exhausts the fireman. If land boilers are 
properly clothed to avoid radiation, and if the fire-room is 
airy and well ventilated, the heat will not be excessive. It is, 
however, very difficult to avoid excessive heat in the stoke- 



98 S TEA M-BO ILERS. 

hole of a steamship. Of course the radiation from the glow- 
ing fuel when the fire-doors are open cannot be avoided, but 
it ought to be possible to clothe the fronts of marine boilers 
more perfectly than is now the common practice. Moreover, 
the ventilation of the stoke-hole is commonly defective ; the 
air pours down through the ventilators and makes cold spots 
immediately beneath them, while other parts of the stoke- 
hole are hot. Forced draught with closed stoke hole usually 
gives good ventilation ; with closed ash-pit it is liable to give 
defective ventilation. 

Grate-bars are commonly made of cast iron, as it is 
cheaper and lasts as well as wrought iron. Sometimes 
wrough-iron bars are used on locomotives and elsewhere, if 
they are expected to withstand rough usage. 

Cast-iron fire-bars are generally 5/8 to one inch thick at the 
top, and 5/16 to 5/8 of an inch thick at the bottom ; they are 
about two inches deep at the ends, and three to five inches 
deep at the middle. To provide for wasting of the upper 
surface, they are made full width for some distance down 
from the top, thus forming a sort of head ; then they are 
rapidly narrowed down to a web that is tapered gradually 
toward the bottom. The space between the bars depends on 
the draught and the nature of the fuel; with ordinary coal 
and natural draught 3/8 to 1/2 of an inch is allowed. Lugs or 
projections are cast at the ends and at the middle, so that the 
bars shall be properly spaced when laid side by side. With 
forced draught the bars may be 3/8 to 9/16 of an inch wide at 
the top, and the distance between the bars may be 1/16 to 1/4 
of an inch. A dead- plate two inches wide should be fitted 
to the furnace-tube of marine boilers to prevent admission of 
air at that place. 

The length of fire-bars should not exceed three feet ; the 
length of a fire-grate may be made up of two or three short 
bars. Bars are commonly cast in pairs, or three or four may 
be cast together, to resist twisting and warping under heat. 



SETTINGS, FUANACES, AND CHIMNEYS. 



99 



The usual form of grate-bar, cast in pairs with lugs at the 
side, is shown in Fig. 38. The herring-bone grate shown in 
the same figure is used for burning fine anthracite coal. The 
figure also shows a special form of grate-bar for burning saw- 
dust. 




PLAIN GRATE 

(STANDARD PATTERN) 




SAW-DUST AND WOOD GRATE 

Fig. 38. 

Wrought-iron fire-bars are formed with a head and web, 
but are of uniform depth, as they are cut from a rolled bar; 
they are bolted together in sets of six, with washers to give 
the proper spacing. For marine boilers they may be 5/16 of 
an inch thick at the top, with spaces 3/16 of an inch wide, or 
less. 

Rocking Grates. — The labor of breaking up the clinker 
which forms on grate-bars, when bituminous coal is used, is 
very much reduced by employing some form of rocking grate. 
On locomotives, where the rate of combustion is high and 
where the fire should always be in good condition, some form 
of rocking grate is considered essential, in American practice. 

In Fig. 39 A and B represent alternate grate-bars which 
are supported at semicircular notches at the ends. CC is a 
cast-iron crank-shaft extending across the furnace at one 
end of the grate-bars. Shallow bars like A rest on cranks 
that are above the line CC\ and deep bars like B rest on 



00 



S TEA M-BOILERS. 



cranks below that line, as shown at a, a', and a", and at b 
and b' . The further ends of the grate-bars rest on another 
crank-shaft like CO ' . At the lower right-hand corner of the 
figure c" represents the end of the crank-shaft and d repre- 
sents an upper crank carrying a shallow bar like A. At g is 
a head to which a lever may be applied to rock the crank- 
shaft. When the crank-shaft is rocked the alternate bars are 
thrown back and forth, and grind up the clinker so that it 
falls through the grate into the ash-pit. 




_^PnPEp^- 





Fig. 39. 

Firing. — Care, skill, and intelligence are required to burn 
coal rapidly and economically. There is a marked difference 
in the ability of trained firemen to make steam with a given 
boiler, and probably there is nothing more wasteful and costly 
than a poor or careless fireman. 

The method to be adopted in firing depends on the type 
of boiler, the kind of coal, and the rate of combustion. Three 
methods of firing may be distinguished : 

Spreading, which consists in distributing small charges of 
coal evenly over the surface of the fire at short intervals. In 
this method the object is to deliver the coal just where it is 
wanted, and then not disturb it. The fire can then be kept 
in just the right condition at all times, and probably the best 
results can be thus obtained, both in absolute quantity of 



SETTINGS, FURNACES, AND CHIMNEYS. IOI 

steam and in economy, provided the coal used is well adapted 
to this method. Care must be taken to have the door open 
as little as possible, or an undue amount of cold air will be 
admitted through the fire-door. 

Anthracite coal should always be fired by spreading", and 
should be disturbed as little as possible after it is thrown in 
place. Unless the fire is urged, very little clinker will be 
formed, and the ashes are readily shaken out by a pick or 
hook run up between the fire-bars. The thickness of the fire 
may vary from four to twelve inches, depending on the size of 
the coal and the strength of the fire. 

Dry bituminous coal, and other bituminous coals, if not 
very smoky and if in small pieces, can be advantageously fired 
in this way. Each shovelful thrown on will give off volatile 
matter, which will burn with the excess of air coming through 
the fuel, and very little smoke will result. 

Side firing consists in covering all of one side of the fire 
with fresh fuel, leaving the other bright. The smoke given 
off from the fresh fuel can then be burned with the hot air 
coming through the bright fire. This method of firing is best 
carried on with two furnaces leading to a common combus- 
tion-chamber; the furnaces are fired alternately, at regular 
intervals, with moderate charges of coal. It is customary to 
admit air through the grid in the fire-door when the fuel is 
giving off gas. 

Coking the coal on a dead-plate, or on the grate just inside 
the fire-door, is perhaps the best way of burning a smoky 
coal. The volatile products driven off from the heap of coal 
near the furnace-door burn with the hot air, coming through 
the clear fire at the rear. As soon as the charge is coked it 
is pushed back and spread over the grate, and a new charge 
is thrown on. 

With bituminous coal the fire should be thicker than with 
anthracite coal: from 6 to 16 inches gives good results. 

The method too often followed by ignorant ana indolent 



102 STEAM-BOILERS. 

firemen, of throwing on as much coal as the furnace will hold 
and then sitting down to wait till the steam-pressure falls, 
needs to be mentioned only to condemn it. 

Mechanical Stokers, feeding coal regularly from a 
hopper, have been invented in a variety of forms from time 
to time. Since the hopper may be made of considerable 
size, manual handling of the coal may be entirely avoided, 
and one man can easily attend to a number of furnaces with 
little labor and exposure to heat. It would appear also that 
a more even and better-regulated combustion may be had 
than with hand-firing. All such devices, which have moving 
parts inside a confined furnace, quickly get out of order 
through the combined action of heat and dust. 

The Roney stoker, shown by Fig. 40 as applied to a 
cylindrical tubular boiler, may be taken as an illustration of 
a mechanical stoker. The grate-bars extend across the fur- 
nace and form a series of steps down which the fuel slides, 
burning on the way down. Each grate-bar is hung on pivots 
at the ends, near the top, and has a rounded lug at the bottom 
that rests in a groove in a rocker-bar, as shown by Fig. 41. 

The rocker-bar has a slow and regular reciprocation de- 
rived from a small steam-engine, which tips the grate-bars so 
that the upper surfaces are inclined downward to make the 
fuel slide, and then rights them to check the motion of the 
fuel. The coal from the hopper falls onto a horizontal plate, 
from which it is pushed forward by a " pusher " that is driven 
by the steam-engine which drives the rocker-bar. The rate 
of feeding the fuel can be controlled by changing the stroke 
of the pusher, and by regulating the number of strokes of the 
pusher and of the rocker-bar per minute. The ashes, clinker, 
and other unburned refuse collect on a dumping-grate at the 
foot of the grate-bars. This grate is shown in normal position 
by heavy lines in Fig. 41, and in the dumping position by 
light lines. 

This grate appears to be well adapted to burn smoky fuel, 



SETTINGS, FURNACES, AND CHIMNEYS. 



103 



as such fuel is well coked at the top of the grate, and the 
volatile parts driven off by coking can burn with the excess 
of air coming through the grate at the bottom. 




If the rate of feed is too fast, it is evident that unburned 
coal will work down onto the dumping-grate, and will appear 



104 



S TEA M-B OILERS. 



in the ashes. If the rate of fuel is regulated so that no coal 
appears in the ashes, the fire becomes thin at the bottom, and 
an excess of air is liable to enter there ; certain tests on this 
grate have indicated such an excess of air, which is the side 
on which the fireman is liable to err, as he may not know 
how much waste he thus occasions, while he can see the coal 
in the ashes. 




Fig. 41. 

Special Furnaces are required for burning various refuse 
material, such as sawdust, tan-bark, straw, and bagasse ; no 
attempt will be made to describe them here. 

When wood is burned on a grate it may be sawn into 
pieces two feet long, and the grate may have the bars spaced 
wider than for coal. Cord-wood can be burned on a brick 
hearth a little longer than the sticks of wood ; the wood ashes 
are small in amount, and are light, so that the draught will 
sweep a large portion of them into a pit beyond the hearth. 
Wood is not now burned for making steam except in remote 
places, unless it be at sawmills and wood-working factories, 
where a large amount of refuse wood is produced in the form 
of slabs, sawdust, shavings, etc. 

Smoke Prevention has become a matter of great social 
importance in cities where much smoky coal is used. Though 
the loss through imperfect combustion of carbon to the form 



SETTINGS, FURNACES, AND CHIMNEYS. 105 

of carbon monoxide may be great, and though there may be 
an appreciable loss if the volatile parts of coal are driven off 
unconsumed, it is a fact that the loss in smoke, even when it 
is dense and black, is not enough to induce coal users to take 
the trouble to prevent the formation of smoke. Not infre- 
quently it has been found that the methods used to prevent 
smoke are accompanied by a loss instead of a gain. For ex- 
ample, smoke burning by the alternate firing of two furnaces, 
leading to a common combustion-chamber, may give a slightly 
greater efficiency if just enough hot air in excess is admitted 
through the clear fire, to burn the gases distilled from the fresh 
charge. If the clear fire must be kept too thin, and thus 
admit a large amount of air, in order that the smoke may be 
burned, there will be a loss of efficiency. Though it is not 
well proved, it is asserted that the mixture of finely divided 
carbon, in the form of smoke, with carbon dioxide may give a 
clear gas with the formation of carbon monoxide, and thus with 
a notable loss. The same difficulties arise when side firing 
and coking are resorted to with smoky fuels. 

One of the most perfect arrangements for smoke prevention 
which has yet been tried, consisted of a detached furnace with 
small grate-area and a deficient air-supply, so that the coal was 
distilled and burned to carbon monoxide ; the resulting hot 
gases were then burned under a steam-boiler. The method 
was suggested by the producer-furnaces used for making gas for 
the open-hearth process of steel-making. The objections are 
the loss of heat by radiation from the detached furnace and the 
space occupied by that furnace. Though reported to be a 
success so far as the prevention of smoke was concerned, it 
does not meet with approval. 

It is a common experience, that when laws against making 
smoke are enforced, users of fuel have chosen to buy anthra- 
cite coal or coke, or in some cases have used crude petroleum 
oil. 

Down-draught Furnaces. — In connection with the sub- 



io6 



S TEA M-B OILERS. 



ject of smoke prevention, attention should be called to down- 
draught furnaces, which have the connection with the chimney 
below the grate. The supply of air is through the fire-door 
to the top of the fire, which has a very attractive appearance, 
as it burns brightly at the upper surface unless obscured by 
fresh fuel. A natural inference is, that the combustion is per- 
fect in a down-draught furnace, and that it should give a not- 
able gain in economy of fuel, but a little consideration shows 
that such a furnace is subject to the same conditions as an 




Fig. 42. 



ordinary furnace. If there is either an excess or a deficiency 
of air, the combustion will be imperfect ; in the latter case, as 
with an ordinary furnace, smoke may appear at the top of the 
chimney. Tests made on a boiler using first an ordinary and 
then a down-draught grate have commonly shown little if any 
advantage in favor of the latter. 

Down-draught furnaces, if properly arranged and fired, can 
be made to burn inferior fuels which have a large amount of 
volatile matter without making much smoke; this may be a 



SETTINGS, FURNACES, AND CHIMNEYS. 



IO7 



matter of great importance in cities where laws against smoke 
are enforced. 

Fig. 42 shows a Hawley down-draught furnace applied to a 
Heine boiler. 

The grate which is shown by Fig. 43 consists of two 
transverse wrought-iron headers at the front and back of the 
furnace, between which are two rows of two-inch tubes, acting 
as grate-bars. The tubes in the lower row are placed under the 
spaces between the upper rows of tubes. Water is supplied 
to the front header by a pipe from the back end of the boiler, 
and steam formed in the tubes and headers is discharged 




Fig. 43. 



through a pipe which enters the drum of the boiler near the 
water-line. The headers are flattened to receive the double 
row of tubes, and are provided with hand-holes for cleaning. 
Opposite each tube of the grate there is a plug in the front 
header which can be taken out when the tube needs cleaning. 
A second grate, with solid bars, is placed beneath the water- 
tube grate, to catch unburned fuel that falls through. 

If a boiler has deficient heating-surface or poor circula- 
tion there may be a direct gain from the use of a water-tube 
grate, as in the down-draught furnace. Such a grate is more 
expensive to install and to repair than the ordinary solid-bar 



I08 STEAM-BOILERS. 

grate. Rocking grates or automatic stoking are of course 
precluded. 

Oil-burning Furnaces have the oil thrown in by sprayers 
or atomizers, and the oil burns in a flame that is about four 
inches in diameter and two to four feet long. The sprayer 
has two conical converging tubes, one inside the other, some- 
thing like the steam and water nozzles of a steam-injector. 
Compressed air or superheated steam is supplied to the inner 
tube, and the oil is drawn through the outer tube and thrown 
into fine spray mingled with air. Compressed air is the 
better, considering proper combustion only, but the great 
convenience of using steam near a steam-boiler has led to its 
common use. The proportions of air and oil may be nicely 
regulated, so that perfect combustion may be secured without 
smoke. 

Thus far oil has been used for fuel mainly at the Caspian 
oil-fields, or on steamers coming from that region. The 
petroleum obtained there gives a large amount of refuse that 
cannot be used for other purposes, and coal, which must be 
brought from a distance, is expensive. In the United States 
■oil has been used for fuel at or near oil-fields, or in cities 
where laws against smoke are enforced, 

The use of oil for fuel on war-ships has received favorable 
consideration from some authorities, the evident advantages 
being the great calorific power of oil and the ease with which 
the fires may be maintained and regulated. The fact that oil 
in tanks may be set on fire by explosive shells has prevented 
any extensive adoption of oil for fuel on war-ships. 

Oil for fuel should be stored in tanks outside the fire-room, 
and if possible the tanks should be lower than the burners. 
The oil is pumped from the tank to the burners as required. 
This is to avoid accidental flooding of the furnace and the fire- 
room with oil, and the attendant danger of conflagration. 
Crude oil is more dangerous than refuse oil, since the former 



SETTINGS, FURNACES, AND CHIMNEYS. IO9 

contains all the volatile components that vaporize at ordinary 
temperatures and form explosive mixtures with air. 

Forced Draught. — When a higher rate of combustion is 
required than can be had with natural draught, resort is had to 
fctrced draught, by aid of which 150 pounds of coal can be 
burned per square foot of grate-surface per hour. 

Three systems of forced draught are in common use, 
namely, with a closed stoke-hole, with closed ash-pits, and in- 
duced draught. 

Induced draught has long been used on locomotives, by 
the action of the exhaust-steam thrown through the smoke- 
stack. The same method is used to some extent on tug- 
boats. This method is simple and effective, but can be used 
only with non-condensing engines. Induced draught may be 
obtained by a centrifugal, or other form of blower, in the 
chimney. It is essential that an economizer should be used 
to cool the gases before they come to the blower. 

On steamships forced draught has been obtained by the 
aid of centrifugal fan-blowers. The method with closed ash- 
pit has been used with success on merchant steamers and 
some war-ships. With this method air drawn from the fire- 
room passes through a blower and is delivered to the ash- 
pit, which has an air-tight door. If the pressure in the ash- 
pit exceeds the resistance to the passage of air through the 
fuel, flame comes out around the fire-door unless it is also 
made air-tight. When the fire-door is opened to throw on coal 
the blast must be shut off from that furnace and all others 
having a common combustion-chamber, or flame will shoot 
out into the fire-room in a dangerous manner. One reason 
why it has not been used on war-ships is the difficulty of 
properly ventilating the many small fire-rooms in which boil- 
ers are placed. 

The closed stoke-hole has been the customary way of get- 
ting a forced draught on torpedo-boats and on other naval 
vessels. The stoke-hole is closed air-tight, admission and 



110 S TEA M-B OILERS. 

egress being through air-locks, and air from without is forced 
in through a centrifugal blower till the pressure exceeds that 
of the atmosphere. When a fire-door is opened to attend to 
the fire, there is a strong inrush of air that is liable to make 
the tube-plates leak. So great difficulty has been experienced 
from this cause, when forced draught has been used with the 
Scotch boiler, that many naval officers doubt its advisability 
for large ships. The success of forced draught on the loco- 
motive and on torpedo-boats with modified locomotive-boilers 
may be attributed partly to the type of the boiler and partly 
to the fact that there is only one boiler and one furnace. 
When two boilers are used on a torpedo-boat, each has its 
own chimney. 

On locomotives the induced draught is frequently equiva- 
lent to a column of water five or seven inches high. Forced 
draught on torpedo-boats has approached those figures, but is 
usually less. Large ships usually have the forced draught re- 
stricted to two inches of water. On account of the resistance 
to the entrance of air to the fire-rooms of war-ships, through 
ventilating shafts, gratings, etc., it has been common to assist 
the draught by running the blowers without closing the air- 
locks. 

Howden's System. — The temperature of gases in the up- 
takes of marine boilers is frequently high, especially when 
forced draught is used. In Howden's system the products of 
combustion pass among horizontal tranverse tubes placed in 
an enlargement of the uptake. Air to supply the fire is 
drawn through these tubes by a fan-blower and is thereby 
warmed, thus saving heat and giving quicker combustion. 
Care must be taken in using this system not to go too far, or 
the fire may become too hot and rapidly burn out the fire- 
grates and do other injury. 

Cleaning Fires. — Three tools are used in clearing the 
grate : they are a long straight bar known as the slice-bar, a 
similar bar with the point bent at right angles to make a 



SETTINGS, FURNACES, AND CHIMNEYS. ill 

hook, and a long-handled rake with three or four prongs. 
The hook may be run along between the grate-bars from 
below, to clear the spaces from ashes and clinker. The slice- 
bar is thrust under the fire on top of the grate to break up the 
cinder; it is used also to stir and break up caking coals. The 
rake is used to haul the fire forward or to draw out cinder. 

To clean a fire the fireman breaks up the cinder with the 
slice-bar and rattles down the ashes ; if necessary, he works 
the fire back toward the bridge and exposes the grate in front, 
which may then be thoroughly cleaned. Then he hauls the 
fire forward and cleans the back end of the furnace. Cinder 
which will not break up and pass through the grate is pulled 
out through the fire-door. Some firemen prefer to clean 
the grate one side at a time. After the grate is cleaned the 
fuel left is spread evenly over the grate and fresh fuel is 
thrown on. The fire should be allowed to burn down before 
cleaning, but a fair amount of glowing coal should be left to 
start a new fire briskly. Before beginning to clean the fire 
the draught should be checked by closing dampers or other- 
wise. 

Green's Economizer. — From time to time attempts have 
been made to get heat from the products of combustion by 
passing them through a feed-water heater, after they leave 
the boiler and before they enter the chimney. The earlier 
attempts to use such feed-water heaters were unsatisfactory, 
because the pipes forming the feed-water heater were soon 
covered with soot, and then became inoperative. Green's 
feed-water heater, or economizer, is made of several sets of 
vertical cast-iron tubes four inches in diameter, placed in a 
chamber between the boiler and the chimney. The feed- 
water is pumped in succession through the several sets of 
tubes, beginning at the more remote, and, finally, it passes 
from the nearer tubes to the boiler. This arrangement brings 
the hottest water in contact with the hottest gases. 

The feature which makes the Green economizer successful 



112 S TEA M-B OILERS. 

is the scrapers, which are arranged in sets, one on each tube. 
By power, from a small steam-engine or elsewhere, the 
scrapers are continually moved up and down on the pipes, and 
so the pipes are kept free from soot and in good condition to 
take up heat. 

As might be expected, this economizer has been found 
to be most successful with boilers that have deficient heatinp - - 

o 

surface. 

Chimneys. — The present state of our knowledge of chim- 
neys and chimney draught is very unsatisfactory. The theo- 
ries given in text-books and elsewhere are not strictly logical 
and are based on insufficient data ; they are of little use in 
proportioning chimneys. On the other hand, there is no sys- 
tematic statement of ordinary practice that can be used in 
designing chimneys. 

A statement will be given, first of the ordinary theories and 
their defects, and second of the information at hand. 

Chimney Draught. — The draught produced by a chimney 
is due to the fact that the gases inside the chimney are hotter 
and consequently lighter than the outside air. Though these 
gases at a given temperature and pressure have a little greater 
specific gravity than air at the same temperature and pressure, 
the difference is not much, and may be neglected in the dis- 
cussion of chimney draught. 

To get an idea of the production of draught by a chimney, 
we may consider the conditions that would exist if a chimney 
were filled with hot air and closed at the bottom by a horizon- 
tal partition or diaphragm. The pressure of the air at the top 
of the chimney, due to the atmosphere above that level, is the 
same on the gases inside the chimney and the air outside. The 
pressure on the diaphragm at the bottom is the sum of the 
pressure at the top of the chimney and of the pressure due to 
the column of hot air in the chimney. At the under side of 
the diaphragm the pressure will be that at the top of the 
chimney plus the pressure due to a column of cold air as high 



SETTINGS, FURNACES, AND CHIMNEYS. 1 1 3 

as the chimney. This difference of pressure is considered to 
be the draught, in all theories of the chimney. It may be 
readily calculated for an assumed set of conditions. For an 
actual chimney the draught or difference of pressure inside 
and outside the chimney may be shown by a U tube partially 
filled with water, and having one end connected to the inside 
of the chimney and the other open to the air. The water 
rises in the leg connected with the inside of the chimney ; the 
difference of level measures the draught. 

Suppose now that a small hole is opened in the dia- 
phragm at the bottom of the chimney : cold air from without, 
under the greater pressure existing there, will enter and will 
force some of the hot air out at the top of the chimney. If the 
air is heated as it enters, to the temperature in the chimney, 
we shall have a continuous flow of cold air into and of hot air 
out of the chimney. Replacing the diaphragm by a grate 
charged with burning fuel, through which cold air enters and 
burns with the fuel, we have the actual conditions of chimney 
draught. 

For an example, we will calculate the difference of pres- 
sures, or draught, if a chimney 100 feet high is filled with air 
(or gas) at 6oo° F., while the temperature outside is 6o° F. 

The weight of a cubic foot of air at 32 ° F. and at the 
average pressure of the atmosphere (14.7 pounds) is about 
0.0807 °f a pound. Now the weight of air at a given pressure 
is inversely proportional to the absolute temperature, that is, 
to a temperature obtained by adding 46o°.7 to the temperature 
given by a Fahrenheit thermometer. Consequently we have 
for the weights of a cubic foot of hot gas and of a cubic foot 
of cold air : 

460.7 4- 32 
Hot gas, 0.0807 X ^ffi- = 0.0375 i 

Cold air, 0.0807 X 46o.7 + 3JL = 0.0764. 
460.7 + 60 



H4 S TEA M-B OILERS, 

A column of hot gas ioo feet high and I foot square will 
weigh 3.75 pounds, and would give that pressure in pounds 
per square foot on a diaphragm at the bottom of the chimney. 
The cold air outside will give a pressure of 7.64 pounds per 
square foot. The difference of pressure or draught will be 

7.64- 3-75 = 3.89 

pounds per square foot, 

or 3.89 -r- 144 = 0.027 

of a pound per square inch. In this calculation the variation 
of the pressure of the atmosphere from 14.7 pounds per square 
inch, and the effect of the reduction of pressure in the chim- 
ney, have been neglected, as they are insignificant. 

To find the draught in inches of water we may consider 
that one cubic foot of water weighs 62.4 pounds. Conse- 
quently a column of water a foot square and which produces 
a pressure of 3.89 pounds per square foot will be 

3.89 -7- 62.4 = 0.0623 
of a foot high, or 

0.0623 X 12= 0.75 

of an inch high. This is the draught that would be shown by 
a U tube if the chimney were closed at the bottom. 

It is convenient to express the difference of pressure or 
draught due to the difference of temperatures inside and out- 
side the chimney in algebraic form as follows: Let T Q be the 
absolute temperature of the freezing-point. Let T c be the 
temperature in the chimney and T a the temperature of the 
air. Let w be the weight of a cubic foot of air at freezing- 
point. Then the weight of a cubic foot of hot air in the 
chimney will be 

T 

t: 



SETTINGS, FURNACES, AND CHIMNEYS. I 15 

and the weight of a cubic foot of cold air outside will be 

T 

The weight of a column of hot air H feet high and one foot 
square will be 

T 

■L c 

and that expression will represent the pressure due to such a 
column of air. The weight of a column of cold air and the 
pressure due to it will be 

T 

T a 

The draught due to a chimney H feet high with the absolute 
temperatures inside and outside T c and T a is then 

This expression gives the draught in terms of pounds per 
square foot. 

All theories of chimney draught that have been proposed 
treat the difference of pressures, inside and outside the 
chimney, as though it were a head producing a flow of a fluid, 
as a head of water produces a flow of that liquid. 

Flow of a Liquid. — In hydraulics, it is shown that we 
may express the relation between the velocity of flow of a 
liquid in a pipe and the head producing the flow, by the fol- 
lowing equation : 



V 2 1 ft 

2g \ VI 



in which h is the head, in feet, of the liquid producing the 
ilow ; V is the velocity in feet per second ; g is the acceleration 



1 1 6 S TEA M-B OILERS. 

due to gravity ; k and k x are coefficients used to express 
the resistance of obstructions like valves, bends, etc. ; / is the 
length of the pipe ; m is the ratio of the area to the perimeter 
of the pipe; and f is the coefficient of friction of the fluid 
against the sides of the pipe. The several coefficients vary- 
with the velocity of flow, the size of the pipe, and the nature 
of the resistance. Experiments in hydraulics have been made, 
and tables prepared, so that the proper coefficients may be 
selected for use with the equation, under any given conditions. 

It is assumed in theories of chimney draught that an equation 
of the same form may be used to express the relation between 
the head, or difference of pressure inside and outside the 
chimney, and the flow of gases through the furnace, flues, and 
chimney. The resistances to the passage of gases through the 
grate and the fuel on it, and through the flues and tubes „ 
may be expressed by aid of coefficients G and C, which are 
like k and k x ; the resistance of friction of the gases against 
the side of the chimney may be assimilated to the last term in 
the parenthesis, replacing / by H. 

The thermodynamic theory of the flow of gases leads to> 
equations which differ fundamentally from the equation for the 
flow of liquids. Only when the changes of temperature and 
pressure are small, can the hydraulic equation be used at all, 
and then the approximation is not good Nevertiieless it may 
be possible to base a working theory of chimneys on the hy- 
draulic equation, provided that the proper constants can be 
derived from experiments, and provided that the application 
of the theory be restricted within limits that are determined 
by proper investigation. 

Peclet's Theory of Chimney-draught— The theory of 
chimney-draught which is commonly given in text-books was. 
proposed by Peclet many years ago. This theory assumes, first, 
that the flow of gases through the furnace-flues and chimney, 
may be represented by an equation like the hydraulic equation 
just quoted; and second, that the head h in that equation 



SETTINGS, FURNACES, AND CHIMNEYS. 117 

may be calculated by dividing the draught, expressed in 
pounds per square foot, by the weight of a cubic foot of hot 
gas. The weight of a cubic foot of hot gas is given by the 

T 

expression w~ t and the draught is given by the expression 

I c 

(T T\ 
wH\ — °— -=£) ; so that Peclet's assumption gives 

.:h = H&-i) (1) 

Replacing the coefficients k and k x in the hydraulic equation 
by C and G, which represent the resistance to the flow of gas 
through the tubes and flues, and the resistance to the flow 
through the grate, we have 

or, solving for V the velocity of the hot gas through the 
chimney, 

v= v^iii 7 ! _ x Y ! ... (3) 



i + G + C+l^) 



in 

If the area of cross-section of the chimney is A square 
feet, the volume of hot gas discharged per second is 

VA, 

and the weight discharged per second is 

W^VA.zv^ 
T< 

sj~* / '7™' f T y \ 1 

,'.W=Aw V^fffK '~T 1 1 " 7WV" (4) 



2 1 8 S TEA M-B OILERS. 

From some experiments on chimneys and boilers Peclet 
gives, in connection with this theory, the following values for 
the coefficients, 

C7 = 12, /= O.OI2, 

under the assumption that from 20 to 24 pounds of coal are 
burned per square foot of grate per hour; the coefficient C 
does not appear in his equation. 

Equation (4) is in the proper form for calculating the 
weight of gas discharged by a given chimney, for which the 
height, area, and perimeter of cross-section are known. If the 
weight of gas to be discharged and the area and perimeter 
are known, the equation for a given case leads to a quad- 
ratic equation for finding the height H, which can readily be 
solved numerically. If the weight of gases is known, and the 
height of the chimney is assumed, then the insertion of linear 
dimensions in place of A and m leads to an equation of the 

fourth degree; but as — - is small compared with I -f- G, a 

solution by approximations can be readily made. 

It is probable that the equation (4) with the given values 
for G and f represented satisfactorily the performance of the 
chimneys which were investigated by Peclet. These chimneys 
provided draught for boilers then in common use in France, 
which boilers were probably either plain cylindrical boilers or 
" double-elephant" boilers. For such boilers the resistance 
is mainly at the grate. On the other hand, the resistance to 
the passage of gases through the tubes of cylindrical tubular 
boilers, locomotive-boilers, and marine boilers is about equal 
to the resistance to the passage of air through the fuel on the 
grate. 

Under the conditions of modern practice in America, the 
equation deduced by Peclet, using his values for /and C7, gives- 
results that do not accord with observations or with commoa 



SETTINGS, FURNACES, AND CHIMNEYS. 1 1 9 

practice. The theory consequently is not valuable for pro- 
portioning chimneys. 

If the weight of gas discharged by a chimney of given 
height and cross-section be calculated successively for differ- 
ent values of T c , the temperature in the chimney, the weight 
will be found to increase with the temperature, until the tem- 
perature becomes about 1000 absolute or about 6oo° F. ; be- 
yond this temperature the weight decreases. 

The temperature for maximum discharge, as calculated by 
the equation, may be readily found by aid of the differential 
calculus. The factor which increases with the temperature is 

T c ' 

Differentiating with regard to T c and equating the first 
differential coefficient to zero gives 

TA(T c -T a )-}-(T e - r a )* = o. 

.'. T c = 2 T a . 

Consequently the maximum discharge of gas will occur 
when the absolute temperature in the chimney is twice the 
absolute temperature of the air. If the temperature of the air 
is yo° F., or 

;o + 460.7 = 530.7 

degrees absolute, then the temperature to produce the maxi- 
mum discharge of gas will be, by Peclet's theory. 

2 x 530°-7 = io6i°.4 absolute, 
or io6i°.4 — 46o°.7 — 6oo°-f F. 

This is about the temperature of melting lead, and 
books on chimneys frequently say that the temperature in a 
chimney should not exceed that of melting lead. A tem- 
perature near this is commonly found in chimneys that are 
doing good work, a fact that seems to give some support to 



1 20 S TEA M-BOILERS. 

the theory. But the support is entirely fictitious, for the oc- 
currence of a maximum depends on the assumption that the 
head h in the hydraulic equation may be replaced by 

IT \ 

H\ — — I j j an assumption that can be justified only by ob- 

servation or experiment. Such observations or experiments 
are lacking. All we know is that calculations by the equation 
do not accord with common practice. It is true that 6oo° F. 
should be a sufficiently high temperature in the chimney to 
give all the draught required. It will be still better if a 
lower temperature will suffice. 

Peclet's Second Theory. — It appears that Peclet was not 
satisfied with his theory as first propounded, for he after- 
wards advanced another theory, in which the head is calcu- 
lated by dividing the draught, expressed in pounds per 
square foot, by the weight of a cubic foot of cold air. It is 
noteworthy that this later theory does not show a maximum 
discharge at 6oo° F. 

Neither the first nor the second theory is strictly logical ; 
the value of either as a working theory must consequently de- 
pend on its adaptability for designing chimneys under condi- 
tions of ordinary practice. Both theories lack connection, 
through experiment or observation, with practice, and can- 
not now be used to advantage. 

Tests and Observations. — The data from the tests made 
by Peclet to determine the values of constants in his equation 
are not now accessible. He gives only the results, namely, 
G = 12 and/ = 0.012. 

Prof. Gale' 55 ' reports the following results of tests made on 
a chimney and boiler of ordinary construction : 

Area of grate 22.5 sq. ft. 

Area through tubes 2.74 " 

Coal per square foot of grate per hour 13.5 pounds. 

Air per pound of fuel 21 " 



* 



Trans. Am. Soc. Mech. Engrs., vol. xi. p. 451. 



SETTINGS, FURNACES AND CHIMNEYS. 



12 



Temperature boiler-room 60 ° F 

Temperature external air }0° F. 

Height of chimney above grate 72 feet. 

Area of chimney (round iron stack) 4 sq. ft. 

Length of horizontal iron flue 24 feet. 

PRESSURES IN POUNDS PER SQUARE FOOT. 

Required to produce entrance velocity 0.013 

Required to overcome resistance of grate 0.91 

Required to overcome resistance of combustion-chamber and boiler-tubes 1.23 

Required to overcome resistance of horizontal flue 0.06 

Required to produce velocity of discharge , 0.085 

Total effective draught 2. 298 

Required to overcome resistance of friction o. 19 

Total draught 2.4S8 

On these results Prof. Gale based a set of constants, to 
be used in an equation like that given in Peclet's first theory. 
It does not appear to us that observations on one chimney are 
sufficient for this purpose. We will note only that his value 
for the coefficient of friction is /= 0.012 for an unlined iron 
stack. For a brick chimney he gives f = 0.016. 

The following table gives the results of a test made at the 
Massachusetts Institute of Technology on an unlined steel 
chimney 3 feet in diameter and 100 feet high above the grate. 



Over the grate 

At the bridge-wall 

Half-way between bridge and back end of 

boiler 

At back end of boiler 

In uptake near boiler 

In stack 34 feet above grate 

1 n stack 5 1 feet above grate 

In stack 68 feet above grate 

In stack 85 feet above grate 



Draught. 
Inches of Water. 


Tempc 
Centi 


Max. 


Min. 


Max. 


0.240 


0.2I8 




O.382 


O.372 




O.410 


0.374 




0-354 


0-334 




O.572 


0.543 


206 


0.440 


O.414 


202 


0.334 
O.216 


O.312 
O.168 


193 

188 


O.I22 


O.OS6 


174 



Min. 



198 
190 

187 
179 
157 



122 S TEA M-B OILERS. 

This chimney now serves two boilers similar to that shown on 
Plate I, each of which is rated at 80 horse-power. It is in- 
tended to be sufficient for four such boilers. The heating- 
surface of each boiler is 11 13, and each has 25.9 square feet 
of grate area. At the time of the test one boiler had the fire 
banked, and the combustion at the grate of the working boiler 
was at the rate of 19.8 pounds per square foot of grate-surface 
per hour. 

Kent's Table.— Mr. Wm. Kent* has calculated a table of 
sizes of chimneys on the following assumptions: 

1. The draught-power varies as the square root of the 
height. 

2. Allowance for friction against the sides of the chimney 
may be made by subtracting from the actual area of the sec- 
tion of the chimney, a strip two inches wide and as long as 
the perimeter "of the section. 

3. The power of the chimney is directly proportional to 
the area remaining after the strip is deducted from the actual 
area. 

The first assumption is equivalent to using the hydraulic 
equation on page 1 1 5 in the simplified form 

^=— or V=V~2jH, 

in which H is the height of the chimney in feet and V is the 
velocity of discharge. 

The second assumption is purely arbitrary, and can be used 
only with.n limits, or it may lead to absurd results. Thus a 
flue 4 inches in diameter would give no draught at all by this 
assumption. 

The third assumption follows naturally from the second. 

If the side of a square chimney be represented by D } then 
the area is 

A =D\ 

* Trans. Am. Soc. Mech. Engs., vol. xi. p. 81. 



SETTINGS, FURNACES, AND CHIMNEYS. \?l 

and the strip to bo subtracted is (nearly) 

4D x tV = i D = 0.6 V7T 

If the effective area allowing for the strip is E, then for square 
chimneys 

E =A -o.6VA~. 

The same equation may be used for round chimneys with 
but little error. 

Combining the first and third assumptions, Mr. Kent writes 
the equation 

H.P. = CE 1/77, 

which he uses for calculating the commercial horse-power of 
the chimney, or more properly of the boilers to be connected 
with the chimney. 

To obtain a value for the arbitrary constant C he chooses 
a typical chimney, 80 feet high and 42 inches in diameter, 
for which the effective area calculated by his method is 9.62 
square feet. He says that such a chimney should be capable 
of carrying a combustion of 120 pounds of coal per hour for 
each square foot of effective area. If the area of the chimney 
is one eighth of the area of the grates connected with it, then 
this is equivalent to a combustion of 120 -^-8 = 15 pounds of 
coal per square foot per hour — a very common performance. 

This typical chimney should then burn 

9.62 X 120 = 1 154.4 

pounds of coal per hour. If it be assumed that nve pounds 
of coal will be burned per horse-power per hour, tne chimney 
may be considered to correspond to 

1154.4-5 =231 H.P. 
Substituting in the formula for horse-power 
231 = C X 9.62^80. 
."• ^=3-33 



124 



S TEA M-B OILERS. 



And the horse-power equation, substituting for E its value, 
may be written 

H.P. = 3-3304 - 0.6 VA) V7T. 

The following table has been calculated by the equation 
just written : 

SIZES OF CHIMNEYS WITH APPROPRIATE HORSE-POWER 
OF BOILERS. 





Height of Chimneys. 


V 


4) 


<*- v 


C <r- 
























'— re "*"■ 


— a! ■** 

2 22 « 


u- O cfl ■ 

° « s * 8 


■ JZ 

re u 


50ft 


60 ft 


70 ft 


80 ft 


90 ft, 


100 ft. 


no ft. 


125 ft. 


150 ft. 


175 ft. 


200 ft. 


u <u v 

CD U !_ 


qj v. •- >U ,e 


Q.S 


























<<3 










Comi 


nercial Horse-powei 








cr 


in a 


18 


23 


25 


27 


















O.97 


i-77 


16 


21 


35 


38 


4i 


















I 


47 


2.41 


19 


24 


49 


54 


58 


62 
















2 


08 


3-i4 


22 


27 


65 


72 


78 


83 
















2 


78 


3-98 


24 


30 


84 


92 


100 


107 


"3 














3 


58 


4.91 


27 


33 




US 


125 


133 


141 














4 


47 


5-94 


30 


3* 




141 


152 


163 


173 


182 












5 


47 


7.07 


32 


39 






183 


196 


208 


219 












6 


57 


8.30 


35 


42 






216 


231 


245 


258 


271 










7 


76 


9.62 


38 


48 








3" 


330 


348 


365 


389 








10 


44 


12.57 


43 


54 








363 


427 


449 


472 


503 


551 






13 


5i 


15.90 


48 


60 








505 


539 


565 


593 


632 


692 


748 




16 


98 


19.64 


54 


66 










658 


694 


728 


776 


849 


918 


981 


20 


83 


23.76 


59 


72 










792 


835 


876 


934 


1023 


1 105 


1181 


25 


08 


28.27 


64 


78 












995 


1038 


1 107 


1212 


1310 


1400 


29 


73 


33-18 


70 


84 












1163 


1214 


1294 


1418 


T 53i 


1637 


34 


76 


38.48 


75 


90 












1344 


1415 


1496 


1639 


1770 


1893 


40 


19 


44.18 


80 


96 












1537 


1616 


1720 


1876 


2027 


2167 


46 


01 


50.27 


86 



The number of pounds of coal per hour that can be burned 
with a given chimney can be found by multiplying the horse- 
power given in the table by five. 

Only that part of the table is filled in which corresponds 
to ordinary proportions, depending on the judgment of the 
author of the method. In general it will be better to select 
proportions from the table for a chimney to be used with a 
given commercial boiler horse-power, rather than to calculate 
by the formula, as extraordinary proportions will then be 
avoided. 

This table hai been used to a considerable extent, and 
apparently with satisfactory results. 

Areas of Chimneys and Flues. — In common practice it 
is found that satisfactory results are obtained if the area of the 



SETTINGS, FURNACES, AND CHIMNEYS. 



12 



section of a chimney is made one eighth of the area of all the 
grates connected to the chimney. The ratio is sometimes as 
large as 1/7 and sometimes as small as 1/9, or for tall chim- 
neys 1/10. 

Height of Chimney. — Professor Trowbridge* gives the 
following table of heights of chimney required to give certain 
rates of combustion, obtained by collecting reliable data and 
drawing a curve to represent mean results: 

HEIGHT OF CHIMNEY. 



Heights in Feet. 


Pounds of Coal per Square 

Foot of Section of Chimney 

per Hour. 


Pounds of Coal per Square 
Foot of Grate per Hour. 


20 


60 


7-5 


25 


68 


8-5 


SO 


76 


9-5 


35 


84 


10.5 


40 


93 


11.6 


50 


105 


13.1 


60 


116 


14.5 


70 


126 


15.8 


80 


135 


16.9 


90 


M4 


18.0 


100 


1^2 


19.0 


no 


160 


20.0 



The table was made several years ago, but it seems to be 
conservative and to represent good average practice. By its 
aid the height of a chimney to give a desired rate of combus- 
tion can be determined. This height is then to be used with 
the ordinary ratio of chimney-area to grate-area as just given. 

Forms of Chimneys.— Chimneys are made of brick or 
of steel plates. Steel chimneys are always round ; large brick 
chimneys are usually round ; small ones may be round or square. 
A round chimney gives a larger draught-area for the same 
weight of material, and it presents less resistance to the wind. 

Plate V gives the general arrangement and some detail of 
two chimneys: one of brick, 175 feet high, and the other of 

* Heat and Heat-engines, p. 153. 



126 STEAM-BOILERS. 

steel, 200 feet high. The brick chimney is built in two parts : 
the outer shell, which resists the pressure of the wind ; and the 
lining, which forms the flue proper, and which may expand 
when the chimney is full of hot gases without bringing any 
stress on the shell. The shell has a foundation of rough stone 
and one course of dressed stone at the surface of the ground. 
The brickwork is splayed out inside to cover the stone foun- 
dation, and is drawn in at the top to the same diameter as the 
inside of the lining. The external form of the top is mainly 
a matter of appearance. The finish of large tiles at the top 
sheds rain and keeps water from penetrating the brickwork. 
The outside of the shell has a straight taper from the base 
nearly up to the head. A system of internal buttresses, as 
shown in section at Fig. 3 and Fig. 4, gives the requisite stiff- 
ness to the shell without an excessive amount cf material. 
The lining carries its own weight only, being protected from 
the wind by the external shell; it has a uniform diameter of 
6 feet inside, and varies in thickness from 12 inches at the 
bottom to 4 inches at the top. A rectangular flue with an 
arched top, leads into the chimney at one side of the founda- 
tion. 

The shell of the steel chimney is made of vertical half-inch 
plates at the base, and is splayed out to give additional bearing 
on the foundation. Above this portion the shell has a straight 
taper to the top ; the plates, each 4 feet wide, vary in thick- 
ness from 3/8 of an inch to 1/4 of an inch. At the top an 
external finish of light plate is given for the sake of appear- 
ance. The foundation is of red brick, with a course of stone 
at the surface of the ground, clamped by a wrought-iron strap. 
The shell is bolted through a foundation-ring made of cast-iron 
segments 4 inches thick, and a steel plate 2j inches thick, by 
long bolts which take hold of anchor-plates bedded in the 
foundation. The lining of fire-brick varies in thickness from 
18 inches at the bottom to 4J inches at the top. It lies against 
and is carried by the steel shell. The internal diameter of the 



SETTINGS, FURNACES, AND CHIMNEYS. 1 27 

chimney is intended to be 10 feet; at places the size is a little 
larger on account of the arrangement of the lining. The lining 
is used to check the escape of heat through the steel shell. 
It adds nothing to the strength of the chimnev ; on the con- 
' trary, it must be carried by the shell There is a chance that 
moisture may be harbored between the lining ana the shell 
and give rise to corrosion. Large steel chimneys are compar- 
atively recent, so that experience does not show whether lined 
or unlined chimneys are the more durable. 

Stability of Chimneys.— On account of the concentration 
of weight on a small area, and the disastrous results that would 
follow from defective work, the founaanons of an important 
chimney should be carefully laid by an experienced engineer. 
A natural foundation is to be preferred, but piling and other 
artificial methods of preparing the earth for the foundation can 
be used when necessary. Good natural earth should carry 
from 2000 to 4000 pounds to the square foot. The base of 
the chimney should be spread out so that this pressure, or 
whatever the earth can safely bear, may not be exceeded. 

In calculating the stability of a chimney it is customary 
to assume the maximum pressure 01 the wind as 55 pounds 
per square foot on a flat surface. The pressure of the wind 
on a round chimney is assumed to be half that on a square 
chimney having the same width. This method has long been 
in use, and it has been shown to give abundant stability. 
Experiments on wind-pressure are difficult and uncertain, and* 
curiously, the pressure determined by small gauges is com- 
monly in excess of that shown by large gauges. Thus, cer- 
tain experiments made during the construction of the Forth 
Bridge, gave a maximum wind-pressure of 35 pounds per 
square foot on a large gauge 20 feet long and 15 feet wide, 
while a small gauge showed a pressure of 41 pounds at the 
same time. The highest recorded pressure during violent 
gales, at the Forth Bridge, was that just quoted, namely, 35 
pounds to the square foot. Small wind-gauges have shown 



128 S TEA M-B OILERS. 

a pressure of 80 to 100 pounds to the square foot; but such 
results are discredited, both because it is known that small 
gauges give too large results, and because buildings were not 
destroyed as they would have been if exposed to such wind- 
pressures. 

To determine whether a chimney is stable, treat it as a 
cantilever uniformly loaded with 55 pounds to the square 
foot and find the bending-moments and resultant stresses. 
The stress will be a tension at the windward side and a com- 
pression at the leeward side. Calculate the direct stress due 
to the weight of the chimney, which will be a compression at 
either side of the chimney. For a brick chimney, subtract 
the tension due to wind-pressure at the windward side from 
the compression due to weight : if there is a positive remainder 
showing a resultant compression the chimney will be stable ; 
otherwise not, because masonry cannot withstand tension. 
Again, add the compression due to wind-pressure to the com- 
pression due to weight, to find the total compression at the 
leeward side : if the result is not greater than the safe load on 
masonry, the chimney is strong enough. The safe load may 
be taken at 8 tons per square foot. A steel chimney may be 
calculated for compression only, since steel is at least as strong 
in tension as in compression. The compression should be 
limited to 10,000 or 12,000 pounds per square inch on the 
net effective section between rivets. The assumption that 
rivet-holes are completely filled by the rivets, and that the 
total compressive strength is not reduced by cutting the rivet- 
holes, is erroneous. The shearing-resistance of the rivets in 
the rinp-'Seam should be made equal to the compressive 
strength of the net section between rivets, in a manner anal- 
ogous to that used for determining the proportions of boiler- 
joints. 

A calculation like that just described must be made for 
the section of the chimney at the base, for each section where 
there is a change of thickness or of construction, and for any 



SETTINGS, FURNACES, AND CHIMNEYS. 1 29 

other section where there is reason to suspect weakness or 
instability. 

The lining of a brick chimney is to be calculated for com- 
pression due to weight, at the base and at each section where 
there is a reduction of thickness. The lining of a steel chim- 
ney must be counted in when the stress due to weight is 
determined. 

A separate calculation must be made for the stability of 
the foundation of a steel chimney. For this purpose find the 
total wind-pressure on the chimney and its moment about an 
axis in the plane of the base of the foundation. Find also 
the total weight of the entire chimney with its lining, and of 
the foundation : this will be a vertical force acting through 
the middle of the foundation. Divide the moment of the 
wind-pressure by the weight of the chimney and foundation : 
the result will be the distance from the middle of the founda- 
tion to the resultant force due to the combined action of 
wind-pressure and weight. If this resultant force is inside 
the middle third of the width of the foundation, the chimney 
will be stable. 

This brief statement is intended to describe the method 
of calculating the stability of chimneys, and not to give fulli 
instructions. The design and calculation for an important 
chimney should be intrusted only to a competent engineer 
who has had experience in such work. 



CHAPTER V. 
POWER OF BOILERS. 

THE power of a boiler to make steam depends on the 
amount of heat generated in the furnace, and on the propor- 
tion of that heat which is transferred to the water in the 
boiler. The amount of heat generated depends on the size 
of the grate, the rate of combustion, and the quality of the 
coal burned. The transfer of heat to the water in the boiler 
depends on the amount and arrangement of the heating-sur- 
face. In practice it is found that each type of boiler has 
certain general proportions which give good results ; any 
marked variation from these proportions is likely to give poor 
economy in the use of coal, or to lead to excessive expense in 
construction. 

The capacity of a boiler is commonly stated in boiler 
horse-power; the economy of a boiler is given in the pounds 
of steam made per pound of coal. Neither method is entirely 
satisfactory, but definite meaning is attached to the terms 
by definitions and conventions. 

Standard Fuel. — A comparison of the composition and 
of the total heats of the several kinds of coal given in the 
table on page 41 shows a great difference in the value of a 
pound of coal, depending on the district and mine from which 
it comes. In order to introduce some system into the com- 
parison of the performance of boilers in different localities it 
has been proposed that some coal or coals be selected as 
standards, and that all boiler-tests intended for comparison 
be made with a standard coal. For this purpose it has been 

130 



POWER OF BOILERS. 131 

proposed to select Lehigh Valley anthracite, Pocahontas 
semi-bituminous, and Pittsburg bituminous coal. More def- 
inite comparisons would result if only one coal, such as Poca- 
hontas, were selected. The objections are, first, that some 
trouble and expense might be incurred in localities where 
this coal is not regularly on the market ; and second, that 
a furnace designed for a given coal may not give its best 
results with a different kind of coal. There is a notable dif- 
ference between furnaces designed for anthracite coal and 
those designed for bituminous coal ; for the rest it appears 
that the use of a standard coal is a question merely of ex- 
pediency. 

In making a boiler-test it is not difficult to make an ap- 
proximate determination of the per cent of ash in the coal 
used. When that is done, the economy is usually stated in 
terms of water evaporated per pound of combustible, as well 
as per pound of coal. This gives somewhat more definite- 
ness to the statement ; but as no account is taken of the vola- 
tile matter in the coal, nor of the oxygen, this method also is 
indefinite. 

Value of Coal. — The actual value of a coal for making 
steam can be determined only by accurate tests with a fur- 
nace and boiler which are adapted to develop and use the 
heat that the coal can produce. While many boiler-tests 
have been made, and there is a good deal of material that 
could be used for the purpose, there has not yet been made a 
satisfactory statement of the value of the fuel in common use. 

It appears probable that the real value of a coal for mak- 
ing steam is proportional to the total heat of combustion. If 
this can be shown to be true, then coals should be sold on the 
basis of heat of combustion, just as steel is required to have 
certain physical properties which are determined by making 
proper tests. 

Quality of Steam. — When the economy of a boiler is 
stated in terms of water evaporated per pound of coal, it is 



\y 






132 S TEA M-B OILERS. 

assumed that all the water is evaporated into dry saturated 
steam. But the steam which leaves the boiler may contain 
some water, or it may be superheated. 

The moisture carried along by steam is called priming. 
The steam from a properly designed boiler, working within its 
capacity, seldom carries more than three per cent of priming. 
Under favorable circumstances steam from a boiler will be 
nearly dry. 

If steam, after it passes away from the water in the boiler, 
passes over hot surfaces it will be superheated ; that is, raised 
to a temperature higher than that of saturated steam at the 
same pressure. Vertical boilers with tubes through the steam- 
space give superheated steam. If steam is to be superheated 
to any considerable extent, it must be passed through a 
superheater, which usually is in the form of a coil of pipe sub- 
jected to hot gases outside. Now a boiler filled with water 
will keep the plates and tubes which form the heating-surface 
somewhere near the temperature of the water; such heating- 
surface will endure service for a long time. But superheating- 
surface is likely to be at a temperature about half-way between, 
that of the steam inside and the gases outside, and is liable to 
be rapidly destroyed. For this reason superheated steam, 
though it gives a notable gain in economy when used in a. 
steam-engine, is not looked upon with favor. 

Steam-space. — The steam-space and the free surface for 
the disengagement of steam should be sufficient to provide for 
the efficient separation of the steam from the water. Cylin- 
drical tubular boilers frequently have the steam-space equal to 
one third of the volume of the boiler-shell. Marine return- 
tube boilers usually have a smaller ratio of steam-space to 
water-space. 

The more logical way appears to be to proportion the 
steam-space to the rate of steam-consumption by the engine. 
Thus the ratio of the volume of the steam-space of cylindri- 
cal boilers to that of the high-pressure cylinder of multiple- 



POWER OF BOILERS. 1 33 

expansion engines varies from 50 : I to 140 : 1. The ratio of 
the steam-space of a simple locomotive-engine to the volume 
of the two cylinders is about 6£ : 1. 

The capacity of the steam-space is sometimes equal to the 
volume of steam consumed by the engine in 20 seconds. It 
was found in some experiments with marine boilers having a 
working-pressure less than 50 pounds per square inch, that a 
considerable quantity of water was carried away by the steam 
when the steam-space was equal to the volume of steam con- 
sumed in 12 seconds, but that no water was carried into the 
cylinders when the steam-space was equal to the volume of 
steam used in 1 5 seconds and that no trouble from water was 
ever experienced when the steam-space was proportioned for 
20 seconds. 

All the preceding discussion refers to engines that run at a 
considerable speed of rotation — not less than 60 revolutions 
per minute. Engines that make but few revolutions per min- 
ute and take steam for only a portion of the stroke require a 
larger proportion of steam-space. As an example we may 
•cite the walking-beam engines for paddle-steamers. 

Equivalent Evaporation.— The heat required to evapo- 
rate a pound'of water depends on the temperature of the feed- 
water, the pressure of the steam, and the per cent of priming. 

For example, if water is supplied to a boiler at 140 F., 
and is evaporated under the pressure of 80 pounds by the 
gauge, with 2 per cent of priming, the heat required will be 
calculated as follows : 

The heat of the liquid at 140 F., or the heat required to 
raise a pound of water from 32 F. to that temperature, is 
108.2 B. T. U. The heat of the liquid at 94.7 pounds abso- 
lute, corresponding to 80 pounds by the gauge, is 293.8 
B. T. U. Consequently the heat required to raise the feed- 
water up to the temperature in the boiler is 

293.8 - 108.2 = 185.6 B.T.U. 

The heat of vaporization, or the heat required to change 



134 STEA M-B OILERS. 

a pound of water into steam, at 94.7 pounds absolute, is 886.9/ 
B. T. U. But 2 per cent of water is found in the steam which 
comes from the boiler, leaving 98 per cent of steam ; conse- 
quently the heat required is 

0.98 X 886.9 = 869.2 B. T. U. 

The total amount of heat is therefore 

185.6 -f 869.2 = 1054.8 B. T. U. 

Suppose that each pound of coal evaporates 9 pounds of 
water, then the heat per pound of coal tranferred to the boiler 
is 

9 X 1054.8= 9493-2 B.T. U. 

Now the heat required to vaporize a pound of water at 2 12° 
F., under the pressure of the atmosphere, is 965.8 B. T. U. 
Dividing the thermal units per pound of coal by this quantity 
gives 

9493.2^965.8 = 9.83, 

which is called the equivalent evaporation from and at 212 F. 

This method of stating the economy of a boiler is equiva- 
lent to using a special thermal unit 965.8 as large as the ther- 
mal unit defined on page 44. 

In making calculations involving quantities of wet steam 
it is convenient to consider the amount of steam present, 
rather than the percent of priming. In the example just con- 
sidered, there are 0.02 of water or priming, and 0.98 of steam. 
The part of a pound which is steam is represented by x. 

If the heat of vaporization at the pressure of the steam in 
the boiler is represented by r, the heat of the liquid at that 
pressure by q, and the heat of the liquid at the temperature 
of the feed-water by q ; and if, further, there are w pounds of 



POWER OF BOILERS. 135 

water evaporated per pound of coal, — then the equivalent 
evaporation is 

w(xr -f q — q ) 
965.8 

The highest equivalent evaporation per pound of coal is 
about 12 pounds, and to accomplish this result about 80 per cent 
of the total heat of combustion must be transferred to the water 
in the boiler. The complete combustion of a pound of carbon 
develops 14,650 B. T. U. ; if all this heat could be applied to 
vaporizing water at 212 F., then the amount of water evap- 
orated would be 

14,650 -i- 965.8 = 15-j- pounds. 

Few, if any, coals have a greater heat of combustion, con- 
sequently this figure may be considered to be the maximum 
equivalent evaporative power of coal. 

Should any test appear to give a larger evaporative power, 
or even a power approaching this result, it may be concluded 
either that there is an error in the test, or that there is a large 
amount of priming in the steam. Some tests of early forms 
of water-tube boilers without proper provisions for separating 
water from the steam, appeared to give extraordinary results; 
which results were due to the presence of a large amount of 
priming in the steam. At that time the methods used for 
determining the amount of priming were difficult and uncer- 
tain, and were frequently omitted in making boiler-tests. 

Boiler Horse-power — It has always been the habit to 
rate and sell boilers by the horse- power. The custom appears 
to be due to Watt, and at that time the horse-power of a 
boiler agreed very well with the power of the engine with 
which it was associated. The traditional method of rating 
boilers, coming down from that time, was to consider a cubic 
foot, or 62^- pounds, of water evaporated into steam, as equiva- 



136 5 TEA M-B OILERS. 

lent to one boiler horse-power. This rating is now antiquated, 
and is seldom or never used. 

It is now customary to consider 30 pounds of water evap- 
orated per hour from a temperature of ioo° F., under the 
pressure of 70 pounds by the gauge, as equivalent to one 
horse-power. This standard was recommended by a com- 
mittee of the American Society of Mechanical Engineers.* 

This standard is equivalent to the vaporization of 34.5 
pounds of water per hour from and at 2 12° F. ; it is frequently 
so quoted. It is also equivalent to 33,320 B. T. U. per hour. 

Since the power from steam is developed in the engine, 
and since the economy in the use of steam depends on the 
engine only, and may vary widely with the type of engine, it 
appears illogical to assign horse-power to a boiler. The 
method appears to be justified by custom and convenience. 

Rate of Combustion. — The rate of combustion is stated 
in pounds oi coai burnea per square foot of grate- surface per 
hour. It varies with the draught, the kind of coal, and the 
skill of the fireman. 

In general a slow or moderate rate of combustion gives 
the best results, both because the combustion is more likely 
to be complete and because the heating-surface of the boiler 
can then take up a larger portion of the heat generated. A 
very slow rate of combustion may be uneconomical, because 
there is a large excess of air admitted through the grate, and 
because there is a larger proportionate loss of heat by radia- 
tion and conduction. It is claimed that forced draught may 
be made to give complete combustion with a small amount of 
air in excess, and that it should give better economy than 
slower combustion. It will be remembered that a small 
amount of carbon monoxide due to incomplete combustion 
will cause more loss than a large amount of air in excess. 

Heating-surface. — All the area of the shell, flues, or 

- Trans., voi. vi, 1881. 



POWER OF BOILERS. I 37 

tubes of a boiler which is covered by water, and exposed 
to hot gases, is considered to be heating-surface. Any 
surface above the water-line and exposed to hot gases is 
counted as superheating-surface. The upper ends of tubes 
of vertical boilers are in this condition. 

For a cylindrical tubular boiler the heating-surface in- 
cludes all that part of the cylindrical shell which is below the 
supports at the side walls, the rear tube-plate up to the brick- 
arch which guides the gases into the tubes, and all the inside 
surface of the tubes. The front tube-plate is not counted as 
heating-surface. 

For a vertical boiler like the Manning boiler (page 10) 
the heating-surface includes the sides and crown of the fire- 
box and all the inside surface of the tubes up to the water- 
line. Surface in the tubes above the water-line is superheat- 
ing-surface. A certain 200-H.P. boiler of this type has 1380 
square feet of heating-surface and 470 square feet of super- 
heating-surface. 

The heating-surface of a locomotive-boiler consists of the 
sides and crown of the fire-box and the inside surface of the 
tubes. 

The heating-surface of a Scotch boiler consists of the 
surface of the furnace-flues above the grate and beyond the 
bridge, the inside of the combustion-chamber, and the inside 
surface of the tubes. 

The effective surface of any tube-plate is the surface re- 
maining after the areas of the openings through the tubes is 
deducted. 

Relative Value of Heating-surface. — A review of the 
kinds and conditions of heating-surface in various kinds of 
boilers, or even in a particular boiler, shows that the value of 
heating-surface varies widely. It does not appear possible to 
assign values to different kinds of heating-surface. We will 
note only that surfaces like the shell of a cylindrical boiler 
over the fire, like the inside of a fire-box, or like the flues of 



138 



S TEA M-B OILERS. 



a marine boiler, which are exposed to direct radiation from 
the fire, are the most energetic in their action. Surfaces 
like combustion-chambers and tube-plates, against which the 
flames play, are nearly if not quite as good. The inside of 
small flues and tubes is less favorably situated, more especially 
as the flame is, under ordinary conditions, rapidly extinguished 
after it enters such a flue or tube. The length of the flame 
in small tubes depends on the draught, and with very strong 
forced draught may extend completely through tubes of some 
length. 

The value of heating-surface in a tube rapidly decreases 
with the length. It is doubtful if there is any advantage in 
making the length of a horizontal tube more than fifty times 
the diameter. Tubes of vertical boilers should have twice 
that length. 

Ordinary Proportions. — The following table gives the 
ordinary proportions of various types of boilers: 



Type of Boiler. 


a 

o 
U 

o| 

a 3 

Pi 


Square Feet of 
Heating-sur- 
face per Foot 
of Grate. 


> 6 

cr> 

hi 

> rt u 
< 


in 


■j u 

rtrs 

IS 

(A 

X 




8 to 12 
8 to 15 

10 tO 20 

j 50 to 120 I 
) average 75 \ 

8 to 15 
35 to 45 

9 to 15 

j 15 to 67 ) 
( average 20 j 


25 to 30 
35 to 40 
*48+ 16 

60 to 70 

40 to 45 
30 

35 to 45 

30 to 40 


8 to 10 

9 to 10.5 
9 to 10.5 

6.7 to 8.5 

9 to 10.5 
7 to 9 

9 to 10.5 

7 to 9 


0.36 
0.30 
0.23 

0.07 

0.30 
0.11 

0.28 

0.22 


7.0 


Cylindrical multitubular. 
Vertical, Manning 


11. 5 

11 .1 

4-5 


Locomotive type, sta- 


12.6 


Scotch marine 


3.3 


Water-tube with cylin- 
der or drum 

Water -tube with sepa- 
rator. . 


11. 

7-3 





* 48 heating-surface, 16 superheating-surface. 

The higher rates of evaporative economy are associated 
with slower rates of combustion and with larger ratios of 
heating-surface to grate- surface. 



POWER OF BOILERS. 1 39 

No attempt is made to distinguish the kind or location of 
heating-surface ; it must be understood that the ordinary ar- 
rangements and proportions for the several types are followed 
if this table is to be used in designing boilers. For example, 
it cannot be expected that heating-surface gained by length- 
ening the tubes of a locomotive-boiler will add materially to 
the efficiency of the boiler. 

This table has been compiled from a large number of ex- 
amples, and may be taken to represent current good practice. 
The last two columns giving the grate-surface and heating- 
surface have been computed on the basis of one horse-power 
for 34.5 pounds of water evaporated per hour from and at 
212° F. 

The tables on pages 140 to 145 give the principal dimen- 
sions of notable merchant steamships, of ships in the United 
States Navy, and of ships in the British Navy. The table 
on page 146 gives the particulars of boilers on the U. S. S. 
Brooklyn, the most recent and powerful American cruiser. 



140 



STEAM-BOILERS. 



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POWER OF BOILERS. 



141 



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142 



S TEA M-B OILERS. 



Name of vessel — 


YORKTOWN. 


Charleston. 


Baltimore. 


San Francisco. 


Length between 
perpendiculars 

Beam 

Mean draught 

Displacement, tons 


\ 


228' 0" 

36' 0" 

14' 2* 

1710 


300' 0" 

46' 0" 
17' 10}" 
3580 


315' 0" 
48' 6" 
19' ioi" 
4500 


310' 0" 

49' \\" 
18' 9" 
4088 


Type of engine... 

Diameter in inches: 
High pressure . .. 

Int. -pressure 

Low-pressure 

Stroke in inches. .. 


I Two, horizon- 
< tal, triple-ex- 
( pansion 

22 

3» 

50 
30 


Two, horizon- 
tal, two-cylin- 
dercompound 

44 

85 

36 


Two, horizontal, 
triple-expansion 

42 
60 
94 
42 


Two, horizontal, 
triple-expansion 

42 
60 
94 
36 


Number and types 
of boilers 


j (4) low cylin- 
( drical 


(6) low cylin- 
drical 


(4) double-ended 
(2) single-ended 


(4) double-ended 
(1) single-ended 


Number and diam- 
eter of furnaces 
in each 


1 


(3) 37' 


<HSt 


D. E. (8) 36" 
S. E. (1) 32" 


D. E. (6) 42" 
S. E. (1) 39" 


Length and diam- 
eter of boilers 


I 


17' 9"x 9 '9" 


19' 3 "x 
(3) xi' 0" 
(3) 11' 6" 


D. E. 17' 8" x 14' 7" 
S. E. 6' 2" x 7 ' 2" 


D. E. 19' 2" x 14' 8" 
S. E. 8'x8' 


Total grate-surface 
usedontrial sq.ft. 


1 


220 


Main 422.2 
Aux. 15 


676 


567.6 


Total heating-sur- 
face used on trial, 
sq. ft. 


( 


8092 


Main 15147 
Aux. 430 


17175 


20134 


Steam-pressure in 


1 


150 


91 




135 


boilers (gauge) 




Air-pressure in fire- 
rooms or ash-pits 
in inches of water 


! 


1.25 


For. 1.6 
Aft. 2.0 


2.09 


2.00 


Revs, of main en- 
gine per minute 


i 


Star. Port. 
157.98 155.94 


Star., Port. 

115.35 113.95 


Star. Port. 
116.42 115.08 


Star. Port. 
125.80 123.83 


Vacuum in con- 
denser, inches of 
mercury 


I 


Star. Port. 
24.84 25.02 


Star. Port. 
26.2 26.1 


Star. Port. 
245 24.3 


Star. Port. 
25.7 26.1 


Indicated horse - 
power total, mean, 
of machinery 


( 


3398-25 


6666.16 


10064.42 


9912.93 


Speed per hour in 
knots 


i 


16.14 


18.19 


19.84 


19.52 


Aggregate I. H. P. 
all main engines 


J 


3205 


6316 


9831 


958i 


I. H. P. per square 
foot of grate, 
based on mean 
I. H. P. 


) 


1542 


15-28 


14.89 


17.46 


Heating - surface 
perl. H. P., based 
on mean I. H. P. 


! 


2.385 


2-337 


1. 710 


2.03 


Condensing - sur - 
face per I. H. P., 
based on mean 
I. H. P. 


i 


1.403 


2.069 


1.26 


1.46 


Mean I. H. P. per 
ton of machinery 


\ 


10.6 


9.6 


iQ'53 


10.84 


Coal per hour per 
square foot of 
grate-surface, lbs. 


1 






44.9, estimated 










Coal per hour per 


f 






3-i5 




I. H. P (pounds) 









POWER OF BOILERS 



43 



Newark. 


Bennington. 


310' 10" 


228' 0" 


49' 2" 
18' 3 i" 
3980 


36' 0" 

14' 0" 

1706 


Two, horizontal, 


Two, horizontal, 


triple-expansion 


triple-expansion 


34 


22 


52 
76 


31 
50 


40 


30 


(4) double-ended 
(1) single-ended 


(4) low cylindrical 


D. E. (6) 43" 
S. E. (2) 32" 


(3) 37" 


D. E. 19' 5" x 13' 6" 
S. E. 7' 11" x 8' io*" 


17' 9" x 9' 9" 


54o 


220 


16737 


8210 


162 


166 


2.25 


2-45 


Star. Port. 


Star. Port. 


127.34 126.66 


150.82 151-03 


Star. Port. 


Star. Port. 


36.0 25.7 


24.0 23.6 


8868.57 


3436.09 


19.00 


1705 


8582 


1 
3333 


16.42 


15.62 


1.89 


2-39 


i-4S 


T -43 


13.08 


10.07 


39.98, estimated 


40.56 


2.43 


2.60 



Monterey. 


Detroit. 


256' 0" 


257' 0" 


59' °J" 
14' 5" 
4000 


37' 0" 
14' 5?" 
2068 


Two, vertical, triple- 
expansion 


Two, vertical, triple- 
expansion 


27 
41 
64 
30 


26.5 
39 

63 
26 


(2) cylindrical, S. E. 
(4) Ward coil 


(3) double-ended 
(2) single-ended 


Cylind. (2)42"; Ward, 
annular grate. 10' 2" 
ext.dia., 3' of" int. dia 


D. E. (4) 42" 
S. E. (2) 42" 


Cylind. io' 7" x n' 2"; 
Ward, 12' 4" height, 
io' 8" diameter 


(2) D. E. 18' i"xii'8" 

(1) D. E. i8' 3 i"xn'8" 

(2) S. E. 9'oi"xn' 8" 


383 


368 


4785 


10978 


155 


171 


3.20 


0.8 


Star. Port. 

162.86 161. 17 


Star. Port. 
170.1 170 1 


Star. Port. 
26.6 26.2 


Star. Port. 
25-1 25.5 


5243-92 


5227.14 


13.60 


18.71 


4987 


5154 


13 68 


14.21 


2.81 


2.10 


1.46 


1.46 


13.00 


11.29 











144 



S TEA M-B OILERS. 



Name of vessel. 



Length between 
perpendiculars 

Beam 

Mean draught 

Displacement, tons. 

Type of engine — 

Diameter in inches : 

High-pressure .. . 

Int. -pressure 

Low- pressure 

Stroke in inches 

Number and type I 

of boilers f 

Number and diam- | 
eter of furnaces -{ 
in each 

Length and diam- J 
eter of boilers j 



Total grate-surface ( 
usedontrial, sq.ft. f 



New York. 



380' o" 

64' 3" 
23' lof" 
8480 
Vertical, triple-expan- 
sion, two engines on 
each shaft 

3 2 

47 

72 

42 
(6) double-ended 
(2) single-ended 

D. E. (8) 39" 
S. E. (2) 33" 



D. E. 18' o"xi5' q' 
S. E. 8' 6" x 10' o" 



Machias. 



ur~ ) 
ial, V 

1 
il 



Total heating-sur 
face used on trial 
sq. ft. 

Steam - pressure in | 
boilers (gauge) f 

Air-pressure in fire 
rooms or ash-pits 
in inches of water 

Revs, of main en- \ 
gine per minute f 

Vacuum in con- 1 
denser, inches of V 
mercury \ 

Indicated H.-P., | 
total, mean, of V 
machinery ) 

Speed per hour in ) 
knots j 

Aggregate I. H. P. (. 
all main engines ( 

LHP. per square] 
foot of grate, ' 
based on mean 
I. H. P. 

Heating - surface] 
per I. H. P., based I 
on mean I. H. P., f 
sq. ft. J 

Condensing - sur - 
face per I. H. P., 
based on mean 
I. H. P., sq. ft. 

Mean I. H. P. per 
ton of machinery 

Coal per hour per j 
square foot of 
grate-surface, lbs. ' 

Coal per hour per 
I. H. P. (pounds) 



19c o ' 

32' o" 

12' of" 
1067.5 

Two, vertical, 
expansion 



15-75 
22.5 
35 
24 



1052 
32958 

176 



Main fire-room 2.02 
Aux. fire-room .7 


0.47 


Star. Port. 
134.6 13500 


Star. Port. 
218.55 214.27 


Star. Port. 

253 25.5 


25-7 


17401.42 


1873.41 


21.00 


15.46 


16947 


1794 



16.54 
1.89 

i-35 
"•37 



triple- 



Massachusetts. 



(2) marine locomotive 

, J 6' 9" long 

^ 2 ' I 44" and 54" wide 

18' 6" x 9 ' 3" 



163 



15-61 
a-45 

1.20 

11.98 

38.08 

2-44 



348' o" 

69' 3" 

24' -" 
10265 

Two, vertical, triple- 
expansion 

34^ 

48 

75 

42 
(4) double-ended 
(2) single-ended 

D.E.(8) 4 o" out., 36" in.. 
S.E. (2) 37 " out. ,33" in. 



D. E. (4) i8'xi 5 ' 

(2) 8' 6''xio' -H" 



616 
19194.6 

163.0 
•9935 



.ar. 
132.3 


Port. 
i3i-° 6 


Star. 
25-5 


Port. 
25.2a 


10402 


66 


16.208 


10127 





16.9 



X.84 



X.298 



POWER OF BOILERS. 



145 



Brooklyn. 


Olympia. 


Columbia. 


Minneapolis. 


400' 6'' 


340 o' : 


4«' 7i" 


4»' li" 


6 4 ' *i" 
21' 10 i" 


53'of'atload water-line 
20' 8f" 


58' 2}" 
22' 5" 


58' *i" 
22' 6" 


8150 


5586 


7350 


7387-5 


Four, vertical, triple- 


Two, vertical, triple- 


Three, vertical, triple- 


Three, vertical, triple- 


expansion 


expansion 


expansion 


expansion 


3*ti 

46J§ 


42 
5Q 


42 
59 


42 
59 


72 


92 


92 


92 


42 
(5) double-ended 
(2) single-ended 


42 
(4) double-ended 
(2) single-ended 


42 
(8) double-ended 
(2) single-ended 


42 
(8) double-ended 
(2) single-ended 


D.R.(8)44 // out.,4o // in. 
S.E.(4)42J // out.,4o // in. 
Greatest outside and 
least inside diameters 


D.E.(8) 43 ' out. ,39" in. 
S.E.(4) 43" out., 39" in. 


D.E.(8)43"out., 39 " in. 
S.E. (2) 43" out. ,39" in. 


D.E.(8) 43" out., 40" in. 

(8) 42" out., 39" in. 

S.E. (2) 37" out. ,33" in. 


D. E. ( A ) i8'xi6' 3" 
(0 W 11*" x 
16' 3" 
S. E. ( 2 )9 / 5 // xi6 / 3" 


D. E. (4) 21' 3" x 15' 3" 
S. E.(2)I0' ni" x 15' 3" 


D. E. (6) 18' x 15' 9" 
D. E. (2) 18' x 15' 3" 
S. E. (2) 8' 6 ' x io' ilf" 


D. E. (6) 20' x 15' 9" 
( 2 )i8'x 15 ' 3" 
S E. (2) 8' 6" x 10' i|" 


1016.2 


824 


1408 in first half of trial 
1344 in last half of trial 


1456.2 


33432 


28298.6 


45221 


48194 


158.3 


166.53 


147.2 


150-3 


2.26 


2.04 
Star. Port. 


•73 
Star. Centre. Port. 




Star. Port. 


Star. Centre. Port. 


136.2 136.9 


139.98 138-53 


134.0 127.68 132.9 


131.95 132.19 133. 1 


Star. Port. 


Star. Port. 


Star. Centre. Port. 


Star. Centre. Port. 


25-5 24.9 


24.94 25.59 


25.1 25 25.6 


25.11 25.31 24.76 


18769.62 


17313.08 


18509.24 


20862.3 


21.912 


21.686 


22.8 


23-073 


18248 


16850 


17991 




18.47 


21. Oil 


13.46 


14.29 


.56 


1-635 


2.39 


2-315 


.81 


1. 152 


Star. Centre. Port. 
1.43 1.63 i-7°4 


1.431 


6 




9-57 


10.61 




44.7 
2.19 















1 46 S TEA M-B OILERS. 



BOILERS OF THE U. S. STEAMSHIP BROOKLYN. 



Five Double-ended Boilers (160 lbs. pressure). 

Length in feet and inches (4) 18' o", (1) 19' n£" 

Outside diameter 16' 3" 

Thickness— Shell and top heads iff 

Heads, bottom £" 

Tube-sheets f " 

Furnaces T 9 F " 

Combustion-chambers (4) in each boiler, thickness T 9 g" 

Depth at top 23" 

Width 84" 

Furnaces — Greatest internal diameter 3' 8" 

Least internal diameter 3' 4" 

Length of grate (4) 6' 4", (1) 6' 6'' 

Number in each boiler, corrugated 8 

Tubes — Outside diameter. 2^" 

Length between tube-sheets (4) 6' 6", (1) 7' 5|" 

Number of ordinary (B.W.G. No. 12) 904 

Number of stay (B.W.G. No. 6) 296 

Spaced vertically a distance of 3^" 

Spaced horizontally a distance of 3$" 

Diameter of rivets in shell-sheets i{|"' 

Of screw-stays between backs of combustion-chambers. i^f-" 

Number and diameter of through upper braces (10) of 2f " 

Through lower braces (2) of 2'' 

Braces around each lower manhole (3) of if" 

Braces from head to back tube-sheet (2) of 2|", (6) of 2" 

Heating-surface — Tubes (4), smaller boilers 

each 4594 sq. ft., large boiler 5286 
Furnace and combustion-chambers, 

each of smaller 842, large boiler 890 
Total each of smaller boilers. . . .5436 sq. ft., large boiler 6176 sq. ft. 

Grate-surface, each of smaller boilers 168.6 sq. ft., large boiler 173.2 sq. ft. 

Area through the tubes 173-2 " 

Over bridge-walls 25.85 " 

Smoke-pipes (3), diameter 7.25 ft. 

Area of all 123.84 sq. ft. 

Height above lowest grates 100 ft. 

Diameter of boiler main stop-valves 10 inches. 

Auxiliary stop-valves 7 " 



POWER OF BOILERS. 1 47 

BOILERS OF THE U. S. STEAMSHIP BROOKLYN.— {Continued.) 

Two Single-ended Boilers (160 lbs. pressure). 

Length 9' 5" 

Diameter outside 16' 3" 

Thickness of shell and top heads Jff" 

Heads, bottom £" 

Tube-sheets f " 

Furnaces T 9 ^" 

Combustion-chambers, each boiler, number 2 

Thickness T 9 g " 

Depth at top 23" 

Width at top 85$" 

Furnaces — Greatest internal diameter 42?-" 

Least internal diameter 40" 

Length of grate 6' 4" 

Number in each boiler (corrugated) 4 

Tubes— Outside diameter z\" 

Length between tube-sheets 6' 4f" 

Number of ordinary (B.W.G. No. 12) 466 

Number of stay (B.W.G. No. 6) 152 

Spaced vertically 3J" 

Spaced horizontally 3. 1 /' 

Diameter of rivets in shell-sheets ii|" 

Screw-stays if ' 

Pitch of screw-stays: horizontally 7§", vertically 7'' 

Number and diameter of through upper braces (10) of 2f" 

Lower braces (3) of if" 

Number and diameter of braces from head to back tube- 
sheet (6) of 2" 

Heating-surface — Tube 2335 sq. ft. 

Furnaces and combustion-chambers 421 " 

Total square feet 2756 " 

Grate-surface 84.3 " 

Area through tubes 13.3 " 

Over bridge-walls 6.4 *' 

Diameter of boiler stop-valves *jV' 

Total for all Boilers. 

Heating-surface — Tube 28,332 sq. ft. 

Furnaces and combustion-chambers 5, 100 " 

Total 33.432 " 

Grate-surface 1016.2 " 

Area through tubes 155.86 " 

Ratio total heating-surface to grate-surface 32.9 to 1 

Ratio total area through tubes to grate-surface 153 to 1 

Ratio total area through tubes to total area smoke-pipes. . . . 1.26 to 1 



CHAPTER VI. 
STAYING AND OTHER DETAILS. 

All plates of a boiler that are not cylindrical or hemispher- 
ical require staying to keep them in shape. For example, 
the cylindrical shell of a cylindrical tubular boiler does not 
require staying, because the internal pressure tends to keep it 
cylindrical. On the other hand, the pressure tends to bulge 
out the flat ends, and they must be held in place against that 
pressure. 

Many different methods of staying will be found in the 
different types of boilers seen in practice, and there are fre- 
quently several ways of staying the same kind of a surface. 
A few methods will be described in a general way. The 
placing of stays and arrangement of details is an important 
part of the design of a boiler, and must be worked out for each 
special design. 

Cylindrical Tubular Boiler. — The parts of the tube-sheets 
at the ends of a cylindrical tubular boiler, through which the 
tubes pass, are sufficiently stayed by the tubes themselves. 
The flat ends above the tubes require staying. Also, if there 
is a manhole at the bottom of the front end, the space thus 
left unsupported requires staying, and there is a corresponding 
space at the back end. 

An elaborate set of tests was made by Messrs. Yarrow* and 
Co., to determine the holding-power of tubes expanded into 
a tube-sheet. It was found that from 15,000 to 22,000 pounds 



* London Engineering, Jan. 6, 1893. 

148 



S TA YING A ND THER DETAIL S. 1 49 

were required to pull out a two-inch steel tube ; in some cases 
the tube gave way by tension inside the head into which it 
was expanded. 

The staying of a flat surface consists essentially in hold- 
ing it against pressure at a series of isolated points, which are 
arranged in a regular or symmetrical pattern. A simple case 
of staying is found in the side sheets of a locomotive fire-box. 
Here the stays, which are arranged in horizontal and vertical 
rows, are screwed and riveted. If possible, the pitch or dis- 
tance between the supported points should be the same, but 
this is possible only when arranged in rows as just men- 
tioned. The allowable pitch depends on the thickness of 
the plate. For cylindrical tubular boilers the pitch of the 
supported points of the flat ends above the tubes is 3.5 to 5 
inches. The outside fibre-stress in the plate stayed may be 
from 6000 to 8000 pounds per square inch ; the calculation of 
this stress involves a knowledge of the theory of elasticity, and 
will be referred to later. 

It is not advisable, for this type of boiler, to assign a sepa- 
rate stay to each supported point of the flat surface under 
discussion, consequently the points are grouped, each point of 
the group being riveted to some support inside the boiler, 
and then the supports are held by proper stays. 

A good method of staying the flat end of a cylindrical 
boiler is shown by Plate I, and also, with some further details, 
by Fig. 44. There are two 6-inch channel-bars of proper 
length, that are riveted to the flat head. The rivets tie the 
plate to the channel-bars and thus support the plate at iso- 
lated points. The channel-bars in their turn are supported by 
stays that run directly through the boiler and have nuts and 
washers at each end. The channel-bars act as beams, and must 
be capable of carrying the load due to the pull on the rivets, 
and the through-stays must carry the loads on the beams. 
A short piece of angle-iron is riveted to the upper side of the 
upper channel-bar; it carries five additional rivets in the flat 



150 



S TEA M-B OILERS. 



head, and adds an additional load to the upper channel-bar. 
The points where the through-stays pass through the head 
are supported directly by the stays through the washers and 
nuts. 

The lower channel-bar is a continuous girder with four spans 
and five supports. The stays form three supports and the 
other two are at the inner edge of the flange of the head. 
The upoer channel-bar is a girder with three spans and four 




— I- 

FRONT HEAD FOR 
84-3" TUBES 

Fig. 44. 



supports. The calculation of the stresses in the channel- 
bars is somewhat unsatisfactory, largely because the support 
at the flange of the head is uncertain ; and this support must 
be left with some flexibility, and consequently with some 
uncertainty, as too great rigidity leads to grooving. 

In arranging such a staying, we begin by determining the 
allowable pitch of the points supported by the rivets, assuming 
them to be in equidistant horizontal and vertical rows. This 
allowable pitch must not be exceeded, but the pitch may be 
made less either horizontally or vertically, or in both ways. 

A space of at least three inches is left between the top 



STAYING AND OTHER DETAILS. I 5 T 

row of tubes and the lowest row of rivets, and a similar space 
is left at the sides. This is to avoid grooving. 

The two upper through-stays are fifteen and a half inches 
apart on centres. They must be wide enough apart to allow 
a man to pass through. 

The stay-rods are upset at the ends so that the diameter 
at the bottom of the threads is greater than the diameter of 
the body of rod. The washer outside the plate may be 
made of copper, in which case it is made cup-shaped so as to 
bear on a narrow ring, and is made tight by calking; or the 
washer is made of iron,' and is bedded in red lead to make 
a joint. Sometimes cap-nuts are used outside the head to 
prevent the escape of steam that may leak around the screw- 
threads. Long stay-rods are sometimes supported at the 
middle. 

A method of staying otherwise similar to that just de- 
scribed, uses two angle-irons in place of a channel-bar. A 
washer of special form is used to give a proper bearing, for 
the inner nut on the through-stay, against the angle-irons. 

Fig. 45 shows a different method of staying for cylin- 
drical boilers. The left half of the figure represents the end 
elevation, and the right half represents a section through the 
manhole; this is a common method for boiler drawings. 
The supported points are arranged in sets of four, and are 
tied to forgings known as crowfeet. Fig. 46 represents such 
a crowfoot with four rivets, known as a double crowfoot ; 
a single crowfoot with only two rivets is shown by Fig. 47. 
When crowfeet are used they may be arranged in various 
patterns , in the example given there is a horizontal row of 
five double crowfeet just above the tubes, and three other 
double crowfeet are arranged in a circular arc. At the ends 
of the arc there are two braces like Fig. 48, which are used 
instead of single crowfeet. From each crowfoot a diagonal 
stay is carried to the boiler-shell. These stays are flattened at 
the farther end and bent to lie against the side of the shell, to 



152 



S TEA M-BOILERS. 



which they are riveted with two or three rivets ; the arrange- 
ment is similar to that of the right-hand end of the brace 




£ 



mm 



ooooo 




oo 



Fig. 45- 



o N 




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FlG - 46. Fig. 47. 

shown by Fig. 48. At the crowfoot the stay has a forked 
head through which a bolt passes under the arch of the 



S TA YING A ND THER DETAIL S. 



153 



double crowfoot. A nut holds the bolt in place and pre 
vents the head of the stay from spreading. 




Fig. 50. 
A combination of channel-bar and crowfeet is shown by 
Fig. 49. The double crowfeet are represented as made of 
boiler-plate, bent up as shown by Fig. 50. 



154 



S TEA M-B OILERS. 



A method of staying, suitable only for boilers which 
work under low steam-pressure, is shown by Fig. 51. Short 
pieces of T iron, arranged radially, are riveted to the head. 
Each T iron is supported from the cylindrical shell by two 




OOOOOO OOOOOO 
OOOOOO OOOOOO 



Fig. 51. 

diagonal stays; one of the stays is represented by Fig. 52. 
One end of the stay is split, and is pinned to the T iron; 
the other end is flattened, and riveted to the shell. 

The shell of a cylindrical boiler, whether it is a tubular or 
a flue boiler, is made of a series of sections or rings. Each 




Fig. 52. 

ring is made of one or two plates riveted along the edge, or 
longitudinal seam. This seam has at least two rows of rivets; 
more complicated joints are commonly used to give more 
strength to the seam. Alternate rings of the shell are made 
smaller so that they may be slipped inside the rings at each 
of their ends. The seams joining adjacent rings are com- 
monly single-riveted. The longitudinal seams are kept above 



STAYING AND OTHER DETAILS. 1 55 

the middle of the boiler, so that they are not exposed to 
the fire. The first ring at the front end is always an outside 
ring, so that the first ring-seam has the outside edge pointing 
away from the fire; there is consequently less liability of 
injury to the seam from the flames that pass under the boiler 
toward the back end. 

Vertical Boilers. — The tube-sheets of a vertical boiler, 
as is evident from inspection of Figs. 5 and 6, are usually 
stayed sufficiently by the tubes. Should the upper tube-sheet 
be much larger than the crown of the fire-box, it may need 
staying between the tubes and the shell. Stays like Fig. 48 
may be used for this purpose. 

The circular fire-box of a vertical boiler is subjected to 
external pressure, and is prevented from collapsing under that 
pressure by tying it to the outer shell by screwed stay-bolts, 
which are put in and set like the stay-bolts for a locomotive- 
boiler. 

Locomotive-boiler. — The parts of a locomotive-boiler 
that require staying are the fire-box and the flat ends. The 
tube-sheets are sufficiently stayed by the tubes, but there is a 
part of the tube-sheet at the smoke-box end and a part of the 
flat end above the fire-box which requires support. The prob- 
lems here resemble those met in staying the tube-sheets of a 
horizontal cylindrical boiler, and similar methods are used. 
Thus in Plate II there are shown eight through-stays, each \\ 
of an inch in diameter. These stays pass through the girder 
staying of the crown-sheet, and have a simple nut and washer 
outside the end-plates of the boiler. At the smoke-box end, 
as shown by Figs. 1 and 3, Plate II, there are two diagonal 
stays taking hold of single crowfeet and running to the middle 
of the barrel. At the fire-box end there are four crowfeet or 
short angle-irons, made by bending up boiler plate ; two are 
shown by the right-hand elevation of Fig. 2 on Plate II. The 
outer crowfeet have five rivets, and the others six. From the 
outer crowfeet diagonal stays run to the shell at the ring just 



1 5 6 S TEA M-B OILERS. 

in front of the fire-box. From the inner crowfeet stays run to 
the middle ring of the boiler. There are also two stays like 
Fig. 48, which run to the shell above the fire-box. Finally, 
there is a crowfoot and stay at the middle of the row of eight 
through-stays, this stay fastening to the two end crown-bars. 

Below the tubes there is a place in the fire-box tube-sheet 
which requires support. This is given by three braces like 
Fig. 48, as shown by Figs. 1 and 2, Plate II. The shell of 
the boiler, shown by this plate, is higher over the fire-box than 
it is at the barrel, and a ring of peculiar shape is required to 
join the two parts together. This ring is cylindrical below and 
conical on top ; at the sides there are flattened spaces which 
require stiffening to prevent them from springing, and thus 
start grooving of the plates. For this purpose there are three 
T irons riveted to the shell at the flattened place mentioned, 
as shown by Fig. 1, Plate II. The upper ends of the T irons 
on opposite sides of the boiler are tied together by transverse 
stays above the tubes. 

Coming now to the fire-box of the boiler represented by 
Plate II, we find that at the front, rear, and sides it is tied to 
the external shell by screwed stay-bolts set in equidistant hor- 
izontal and vertical rows. The holes for these stay-bolts are 
punched or, better, drilled before the fire-box is in place. After 
it is in place and riveted to the foundation-ring a long tap is 
run through both plates, the fire-box plate and the shell, and 
thus a continuous thread is cut in the plates. A steel bolt is 
now screwed through the plates, cut to the proper length, and 
riveted cold at each end. Owing to the screw-thread on the 
bolts, this riveting is imperfect, and likely to develop cracks at 
the edge. The thread should be removed from the middle 
of the bolts, as they are then less liable to crack under the 
peculiar strains set up by the unequal expansion of the fire- 
box and outside shell. 

The stay-bolts are very likely to be cracked or broken on 
account of the expansion of the fire-box; to detect such a 



S TA YING A ND O THER DETAILS. 157 

failure of a bolt, or to show when excessive corrosion has taken 
place, the stay-bolts are often drilled from the outer end nearly 
through to the inner end. In case of failure steam will blow 
out of the defective stay ; serious injury has often been avoided 
by this method. 

The crown-sheet of the fire-box is exposed to intense heat, 
and is covered with only a few inches of water. The problem 
of properly staying this flat crown-sheet without interfering 
with the supply of water to it is one of the most difficult 
problems in locomotive-boiler construction. Figs. I and 2, 
Plate II, show the method of staying a crown-sheet with a sys- 
tem of girder-stays. Above the crown-sheet there are fourteen 
double girders, which are supported at the ends by castings of 
special form, shown by Figs. 2 and 6 ; the castings rest on the 
edges of the side sheets and on the flange of the crown-sheet* 
In addition the girder-stays are slung to the shell by sling- 
stays. At intervals of four and a half inches the crown-sheet 
is supported from the girders by bolts, having each a head in- 
side the fire-box, as shown by Fig. 5, and a nut at the top 
bearing on a plate above the girder. These plates are turned 
down at the ends to keep the two halves of the girder from 
spreading. There is a copper washer under the head of each 
bolt, inside the fire-box, to make a joint. Between the girder 
and the crown-sheet each bolt has a conical washer or thimble 
to maintain the proper distance between the girder and crown- 
sheet. This thimble is wide above to bear 011 the girder, and 
small below to avoid interfering with the flow of water to the 
crown-sheet, and also so as to cover as little surface as possible 
on account of the danger of burning the crown-sheet wherever 
the metal is thickened. The whole system of girders is tied 
together, and the girder nearest the fire-door is tied to the 
outside shell to keep the girders from tipping over. It is evi- 
dent that such a system of staying is heavy, cumbersome, and 
complicated. It is also uncertain in its action, since the equal- 
ization of stresses depends on a nice adjustment of the form 



158 



S TEA M-B OILERS. 



bers of the system, which adjustment is liable to derangement 
from expansion of the fire-box. The girders or crown-bars are 
sometimes run lengthwise instead of transversely, but as the 
fire-box is longer than wide such an arrangement is inferior. 

To avoid the cumbersome method of staying the crown- 
sheet, which has just been described, the fire-box end of the 
boiler has been made flat on top, as shown by Fig. 53. The 




T -t + t + -r -i- f H- -t O O 
4- -t 4 -+■ 4 -f-t—t- 4 4 o o 

+ + 4- 4- + •+ 4- 4- 4- -f +1- 

+ ++ + * -t-f + -+•-»• 4 -t- 
+ ++H-t + 4~4--»-4- + + 
4- 4-4-4- -t 1-4-4- + -f t + 
4-t + 4 + + ■+■ t '"+— t 4 •+ 
4-4- 4- •+ f -+- + •+ •+ -J- 4 •+ 
+ -f + +4-f4 f-t- ++4 
4 -4-4-4 4 4 -M- 4--+- 4 4 
44++ff+ + + 4+ 4, 
+ 4 + tt 4-4-4- +-*-4-fl 
4 4 4-t + +-4— f -t- 4 4-4! 
+ 4 +• ++- H-'+~+-M- + 4+| 




Fig. 53. 



crown-sheet can now be stayed to the outside shell by through- 
stays having nuts and copper washers at each end. The flat 
side sheets of the shell above the fire-box are also stayed by 
through-stays, and there are also three longitudinal through- 
stays in the corners of the shell over the fire-box where it 
protrudes beyond the barrel. This forms what is known as 
the Belpair fire-box, from the inventor. 

Fig. 54 shows an attempt to combine the use of through- 
stays, like those of the Belpair fire-box, with a cylindrical top 
above the crown-sheet. It will be noted that the stays are 
neither perpendicular to the crown-sheet nor radial when they 
pierce the shell, and they must be subjected to an awkward 
side pull at both places. 

The locomotive-boiler represented by Plate III has a 
Belpair fire-box, and shows in addition some peculiarities of 



STAYING AND OTHER DETAILS. 



159 



staying. Thus the flat end-plate above the fire-box has 
four T irons riveted to it. Each T iron is tied to the shell 
by two diagonal stays. Each stay has the usual double 
head at the T iron; the other end lies between, and is pinned 
to the flanges of pieces of plate that are riveted to the shell 
of the boiler. This arrangement is shown by the transverse 




and longitudinal sections through the fire-box. It will be 
noticed that the lower diagonal stays from the end-plate 
interfere with four transverse through-stays. These stays are 



i6o 



S TEA M-B OILERS. 




*>N 






Vh 



cut off and carry short vertical yokes, which are connected 
by two smaller rods, one above and one below the diagonal 
stays. 

The rings forming the barrel of the locomotive are made 
progressively smaller from the fire-box to the smoke-box; the 
slight taper toward the front end of the locomotive is found 
convenient in the design of the machine. 

Fig. 55 shows two ways of making the furnace-mouth of 
a locomotive-boiler. In one way the end- 
plate of the boiler-shell and the corre- 
sponding plate of the fire-box are flanged 
iff^ in the same direction, and are riveted out- 
side of the boiler. In the other case the 
two plates are flanged into the water-space 
and the overlapping edges are riveted. 

Marine Boiler. — The parts requiring 
staying in the Scotch boiler are the flat 
ends, the furnaces, and the combustion- 
chambers. The flat ends above the tubes 
are stayed by through-stays with nuts inside 
and with washers and nuts outside the plate. The boiler 
shown by Fig. 13, page 17, has two rows of through-stays 
— four in the upper and six in the lower row; two of the 
upper row pass through the fitting which carries the steam- 
nozzle. 

It is found in practice that the tube-sheets of a marine 
boiler are not sufficiently stayed by plain tubes expanded 
into the sheets. It is customary to make a portion of the 
tubes thicker than the others, and to provide these thick 
tubes with thin nuts outside the tube-plates, so that they may 
act more effectively as stays. The thick tubes in Fig. 13 are 
indicated by heavy circles. Sometimes every other tube of 
each second row is made a thick tube; that is, something 
more than one fourth of the tubes are stay-tubes. Usually 
the number is fewer than this. 



Fig. 55. 



STAYING AND OTHER DEI' AILS. l6l 

Below the tubes the front plate is supported in part by the 
furnace-flues, and in part by through-stays running to the 
combustion-chamber. There are two such stays above the 
furnaces and three below the furnaces in the middle of Fio- 
13, each if of an inch in diameter. There are also two stays 
2\ inches in diameter, one at each side and above the fur- 
naces. These last stays have one point of attachment to the 
front end-plate, but each has two points of attachment to the 
combustion-chamber. For this purpose the rear ends of the 
stays are bolted to V-shaped forgings, similar to that shown 
by Fig. 56, page 162. 

The furnace-flues are corrugated to stiffen them, and thus 
maintain their form under the external pressure to which they 
are subjected. The corrugations in Fig. 13 are made up of 
alternate convex and concave semicircles; other forms of 
corrugations and other methods of stiffening flues, together 
with a discussion of the strength of flues, will be given in the 
next chapter. The front ends of the furnace-flues in Fig. 13 
are made as large as the outside of the corrugations; the rear 
ends are as small as the inside of the corrugations. Such an 
arrangement makes it easy to remove the furnaces without 
disturbing the other parts of the boiler and without destroy- 
ing the flues. 

The combustion-chambers of a Scotch boiler are made up 
of flat or curved plates subjected to external pressure, and 
must be stayed at frequent intervals to prevent collapsing. 
The sides and bottom of the combustion-chamber in Fig. 13 
are stayed to the cylindrical shell of the boiler by screwed 
stay-bolts, spaced seven inches on centres. The back of the 
combustion-chamber is stayed in like manner to the back end 
of the boiler, and thus both of these flat surfaces are secured. 
The plates used for making the combustion-chamber are 
thicker than those used for a locomotive fire-box, and conse- 
quently the stays are spaced wider and are larger in diameter. 
The top of the combustion-chamber is staved by stay- 



1 62 



S TEA M-B01LERS. 



bolts and bridges in a manner that suggests the crown-bar 
staying of a locomotive fire-box. The space is, however, 
narrower and the staying is less complicated. 

Complex Stays. — Sometimes the points to be connected 
by stays are so numerous that too many through-stays will be 




-» 



Fig. 56 



required if all points are stayed separately. Thus in Fig. 56 
there is an angle-iron riveted to a flat plate, and supported 
at intervals, as indicated by the two bolts passing through 
it. Instead of using a through-stay for each bolt, the bolts 
are coupled by two V-shaped forgings, which forgings are 
bolted to a through-stay at the angle of the V. There 
is enough freedom of the bolts in their holes to give equal 
distribution of the pull on the through-stay. By an exten- 
sion of this method several points may be supported by one 
stay-rod. 

Gusset-stays. — The flat ends of the Lancashire boiler, 
shown by Fig. 3, page 6, are secured to the cylindrical shell 
by gusset-stays; such a stay is shown more in detail by Fig. 
57. A plate is sheared to the proper form, and is riveted 



S TA YING A ND O THER D E TA IL S, 



•65 



between two angle-irons along the edges that come against 
the shell and the flat end. The angle-irons in turn are riveted 
to the shell or to the flat plate. Gusset-stays have the 
advantages of simplicity and solidity. They interfere less 
with the accessibility of the boiler than through-stays or 
diagonal stays. Their chief defect is that they are very rigid 
and are apt to localize the springing of the flat plates, which 




Fig. 57. 

is caused by unequal expansion of the furnace-flues and shell. 
Consequently, grooving near gusset-stays is very likely to be 
found in Lancashire and Cornish boilers. Gusset-stays are 
also used to some extent in marine boilers, and in locomo- 
tive-boilers. 

Spherical Ends. — The ends of cylindrical boilers, or of 
steam-drums, are commonly curved to form a spherical sur- 
face, in which case they retain their form under internal 
pressure and do not need staying. If the radius of the 
spherical surface is equal to the diameter of the cylindrical 
surface, the same thickness of plates may be used for both. 
If the spherical surface has a longer radius, the thickness may 
be increased. Such disJicd heads of boilers and steam-drums 
are struck up between dies while at a flanging heat, and are 
then flanged to give a convenient riveting edge. 

Steam-domes are short, vertical cylinders of boiler-plate 
fastened on top of the shell of horizontal boilers. Plates II 
and III show steam-drums on locomotive-boilers. A steam- 
drum may be used to advantage when the steam-space is so 
shallow that there is danger that the ebullition may throw 



1 64 S TEA M-B OILERS. 

water into the pipe leading steam from the boiler. "Locomo- 
tives usually have steam-domes, for not oniy is the steam- 
space shallow, but there is danger of splashing of the water 
in the boiler, especially if the track is rough or sharply 
curved. 

Stationary boilers ought to have steam-space enough with- 
out domes; marine boilers sometimes- have domes, but they 
are less common than formerly. The additional steam- 
volume in a steam-dome is insignificant, so that a dome should 
not be added to increase steam-space of a boiler. 

The main objection to a steam-dome is that it weakens 
the boiler-shell, which must be cut away to form a junction 
with it. The shell may be reinforced, to make partial com- 
pensation, by a ring or flange of boiler-plate. Such a flange 
is clearly shown on Plate III, where the longitudinal seam of 
the ring carrying the dome is purposely placed at the top of 
the boiler. A similar arrangement is made for the dome on 
Plate II. 

Dry-pipe. — Any pipe inside of a boiler for the purpose of 
leading steam from the boiler is known as a dry-pipe; the 
pressure in such a pipe is frequently less than that of the 
steam in the boiler, consequently there is a tendency to dry 
the steam in the pipe. Dry-pipes are found in locomotive 
and marine boilers and sometimes in stationary boilers. 

The dry-pipe of a locomotive opens near the top of the 
dome. It runs vertically down till it is well below the shell 
of the barrel, then it runs horizontally through the steam- 
space and out through the smoke-box tube-sheet. The 
throttle-valve is at the inlet of the dry-pipe. It is controlled 
through a bell-crank lever by a rod which enters the head of 
the boiler from the cab. 

The marine boiler shown by Fig. 13 has a dry-pipe which 
is joined to a steam-nozzle at the front end of the boiler. 
This dry-pipe is pierced with numerous longitudinal slits on 



STAYING AND OTHER DETAILS. 



l6$ 



the upper side; the sum of the area of such slits is seven 
eighths of the area. through the stop-valve in the steam-pipe. 

Steam-nozzle. — The stationary boiler shown on Plate I 
has a cast-iron steam-nozzle at each end. The steam-pipe 
leading steam from the boiler is bolted to the rear nozzle, 
and the safety-valves are placed above the front nozzle. 

Nozzles are often made of cast steel. The best are forged 
without welds from one piece of steel. 

Manholes. — A manhole should be large enough'to allow 
a man to pass easily inside the boiler. That on Plate I is 
fifteen inches long and eleven inches wide, and has its greatest 
dimension across the boiler. 

The manhole there shown is placed inside the shell of the 
boiler. Both the ring and the cover are forged from steel 
without a weld. Fig. 58 shows a form of manhole that is 




Fig. 58, 



placed outside the shell. This form is commonly made of 
cast iron, but cast steel manholes of similar form are used to 
some extent. 

The manhole-ring should be strong enough to give com- 
pensation for the plate cut away from the ring on which it is 
placed. 

The manhole-cover is placed inside the ring so that it is 
held up to its seat by the steam-pressure. The cover is 
drawn up to its seat by a bolt and removable yoke. Some- 



1 66 STEAM-BOILERS. , 

times there are two bolts each with its yoke. A cast-iron 
manhole naturally has a cast-iron yoke, and a forged manhole 
has a wrought-iron or steel yoke. 

The manhole-cover is made steam-tight by a rubber 
gasket; the form of the cover and its seat are such that the 
gasket cannot be blown out by the pressure of the steam. 

Hand-holes are provided at various places on boilers to 
aid in washing out and cleaning. Thus the boiler on Plate I 
has a hand-hole near the bottom at each end, and there are 
several hand-holes near the foundation-ring of the vertical 
boiler, shown by Fig. 5. The hand-hole covers on Plate I are 
placed directly against the plate which is not reinforced. Each 
is held up by a bolt and a small yoke, which has a bearing on 
the plate completely round the hole. If the yoke has insuffi- 
cient bearing on the plate, the latter is liable to be damaged 
and leaks will occur. The hand-holes on the marine boiler 
shown by Fig. 13 are reinforced by small plates outside the 
boiler-heads. 

Washout Plugs. — Instead of hand-holes, washout plugs, 
two inches or two inches and a half in diameter, are provided 
near the corners of the foundation-ring of a locomotive fire- 
box. Such plugs are simply screwed into the outside plate 
of the boiler. Examples are shown by Plates II and III. 

Methods of Supporting Boilers. — Horizontal cylindrical 
boilers are commonly supported on the side walls of the brick 
setting, by brackets which are riveted to the shell of the 
boiler. Thus the boiler shown on Plate I has two such 
brackets on each side; this boiler is about sixteen feet long. 
If a boiler is as much as eighteen feet long, three brackets 
are used. The front brackets rest directly on the brickwork, 
but the other brackets rest on iron rollers, to provide for the 
expansion of the boiler. The brackets are set so that the 
plane of support is a little above the middle of the boiler. 

Fig. 59 shows a common form of bracket, made of cast 
iron, which is riveted to the shell above the flange of the 



STAYING AND OTHER DETAILS. 



I6 7 



bracket. A better form with rivets both above and below 
the flange is shown by Fig. 60. 













00 



00 










Fig. 39. Fig. 60. 

A detachable bracket, like that shown by Figs. 61 and 
62, may be used when the boiler must be put into a building 







© 


J - 

© 





@ 



n v\ 




Fig. 61. 
through a small aperture. 



Fig. 62. 
Fig. 61 gives an end and side 



elevation and plan of the body of the bracket ; Fig. 62 gives 





Fig. 63. Fig. 64. 

a side elevation and plan, with section, of the flange. After 
the boiler is in place the flange is thrust up into the dovetail 



1 68 



S TEA M-BOIL ERS. 



groove in the body of the bracket. The pressure of the flange 
against the dovetail groove, intensified by the wedging action 
of the inclined sides, is liable to be excessive. To overcome 
this difficulty the bracket shown by Figs. 63 and 64 is oftea 




Fig. 65. 



r 


1 


A 


\ 


; 1 


"6" 














Fig. 67. Fig. 69. 

used. Fig. 63 shows the end elevation and a view from 
below, of a casting which is riveted to the shell. Fig. 64 
shows the same views of a casting which catches into the 
hollow under Fig. 63 and bears at the top against this same 
casting, the rivets bolting it to the shell being countersunk. 



STAYING AND OTHER DETAILS. 1 69 

Horizontal boilers, and especially plain cylindrical boilers, 
are sometimes hung from a support above the boiler, as shown 
by Figs. 65, 66, and 67. 

Fig. 65 shows a lug, made of boiler-plate, riveted to the 
shell of the boiler. The lugs are placed in pairs and the 
boiler is hung from these lugs by bolts that are supported 
between transverse beams over the boiler. Fig. 66 differs in 
substituting a loop for the lug. 

Fig. 67 shows a method of suspension with two short 
pieces of plate above the lug, to give some flexibility and 
provide for expansion. 

Figs. 68 and 69 show methods of suspending a boiler from 
the top. These methods are proper only for boilers which 
have a small diameter. 



CHAPTER VII. 
STRENGTH OF BOILERS. 

The determination of the thickness of boiler-plates, the 
size of stays, and other elements affecting the strength of a 
boiler, involves a knowledge of the properties of the materials 
used and a knowledge of the methods of calculating stresses 
in the several members of the boiler. A brief statement of 
these subjects, as applied to boilers, will be given here. 

Materials Used. — The materials used for making boilers 
are mild steel, wrought iron, cast iron, malleable iron, copper, 
bronze, and brass. 

In order to insure that materials used for making a boiler 
shall have the proper qualities, it is customary to require that 
specimens shall be tested in a testing-machine, and that they 
shall have certain definite properties, such as ultimate tensile 
strength, elastic limit, and contraction of area at fracture. 
In order that these properties shall be properly developed, it 
is essential that specimens shall be of right size and shape, 
and that the testing shall proceed in a correct method. 

Testing-machines. — The frame of a testing-machine 
carries two heads, between which the test-piece is placed, and 
to which it is fastened by wedges or other clamping devices. 
One head, called the straining-head, is drawn by screws or by 
a Jiydraulic piston, and pulls on the test-piece. The other 
head, called the weighing-head, transmits the pull to some 
weighing device. Boiler materials are commonly tested in a 
machine which has the pull applied by screws, driven through 
gearing by hand or by power; the pull is weighed by a system 
of levers and knife-edges, arranged like those of a platform 

170 



STRENGTH OF' BOILERS. *7 l 

scale. Such a machine should be able to exert a pull of fifty 
or a hundred thousand pounds. 

Testing-machines that give a direct tension are commonly 
arranged to give also a direct compression. There are also 
machines arranged to give transverse loads, like the load 
applied to a beam. 

Forms of Test-pieces. — A test-piece of boiler-plate 
should be at least one inch wide, planed on both edges, and 
should be about two feet long. A piece which is loss than 
eighteen inches long is not fit for testing. 

Test-pieces eighteen inches to two feet long may be cut 
directly from bars or rods for making stays or bolts. If a rod 
is so large that the available testing-machine will not break- 
it, it is of course possible to turn it down to a smaller 
diameter, but it would be preferable to send such a rod to a 
machine that is powerful enough to break it at full size. 

Test-pieces of cast metal may be cast in the form of 
rectangular bars, which should be at least one inch wide and 
an inch thick. If the bars are rough or irregular it may be 
necessary to plane the edges, or perhaps to plane them all 
over. 

Test-pieces of boiler-plate should be cut from the edge 
of at least one plate of each lot of plates. Sometimes speci- 
fications require pieces from each plate used for a given boiler. 
Pieces should be cut from both the side and the end of a 
plate, for there is a grain developed by rolling either iron or 
steel boiler-plate, and tests should be made both with the 
grain and across the grain. 

Very hard material may require shoulders on the test- 
pieces to enable the testing-machine to get a proper hold. 
But iron or steel that is so hard as to require shoulders is 
much too hard for boiler-making; consequently there will be 
no reason for providing test-pieces of boiler iron or steel with 
shoulders. If test-pieces have shoulders, they should be at 
least ten inches apart. 



172 



STEAM-BOILERS. 

Methods jrf Testing.— A test-piece of proper length is 

first measured to determine the 
breadth and thickness or else the 
diameter, as the case may be. 
A length of eight inches is laid 
off near the middle of the test- 
piece, and clamps for measuring 
the stretch of the piece are ap- 
plied at the ends of this eight-inch 
length, as shown by Fig. 70. 
The piece is then secured in the 
machine and a load is applied. 
The distance between the clamps 
is now measured by a micrometer 
caliper with an extension-piece. 
The method of doing this is to 
place the head of the micrometer 
against a point on the flange of 
the clamp at one end, and adjust 
the length of the micrometer so 
that it shall just touch the cor- 
responding point on the other 
clamp. A little practice will en- 
able the observer to measure to 
one or two ten -thousandths of an 
inch. As the load is increased 
the test-piece stretches, the in- 
crease of length being proportion- 
al to the increase of the load. The 
stretch is measured on both sides 
of the test-piece for each increase 
of load applied. If the test-piece 
is not straight or exactly aligned 
in the machine there may be some 
irregularity in the stretching at 




Fig. 70. 



STRENGTH OF BOILERS. 1 73 

first, but after a considerable load is applied the piece 
stretches uniformly until about half the maximum load that 
the piece can carry has been applied. During the progres? 
of the test a point is reached beyond which the stretch in 
creases more rapidly than the load; this is known as the 
elastic limit. 

After the elastic limit is reached the clamps are removed 
and the test proceeds without them, but at about the same 
rate of loading. A load is soon reached which the piece 
cannot permanently endure, shown by the fact that the scale- 
beam will fall though the straining-head remains at rest. 
This is called the stretch limit. The piece may, however, 
carry a considerably higher load if the straining-head is kept 
moving to take up the stretch. Finally, the piece begins to 
draw down rapidly, somewhere near the middle of its length, 
and when the piece breaks, the fracture shows about half the 
area of the piece before testing. Hard materials may draw 
down little, or not at all; the limit of elasticity may approach 
the strength of the material. 

The jaws or wedges of the testing-machine interfere with 
the stretching or flow of the material gripped by them. The 
influence of the wedges may extend two or three inches 
beyond their edge in the testing of boiler-plate. If a piece 
has shoulders they will have a like effect. Consequently the 
points at which a clamp is secured to a test-piece should be 
two or three inches from a shoulder or from the wedges of the 
machine. The wedges of a machine of a capacity of fifty or 
a hundred thousand pounds are four or five inches Ion"". 
They will grip on three inches at the end of a test-piece, but 
not on less. The test-piece must have eight inches for 
measuring stretch, two or three inches at each end for flow, 
and three to five inches at each end in the wedges. Conse- 
quently the piece must be eighteen or twenty-four inches 
long. 

The method just described is slow and laborious, and 



774 S TEA M-B OILERS. 

requires two observers — one to measure stretch and one to 
weigh. For commercial work an automatic device is often 
used which registers loads and corresponding elongations. 
Such devices commonly record the stretch limit instead of the 
elastic limit; these two points should never be confused. 

Stress. — The number of pounds of force per square inch 
is called the stress. The stress is uniform on a piece under 
direct tension, and is equal to the load divided by the area of 
transverse section. Stress may be expressed in other units, 
such as tons per square foot or kilograms per square milli- 
meter. 

Strain. — The stretch of a piece, under direct tension, per 

unit of length is called the strain. If the original length is / 

. . # 
and the stretch is a, then the strain is - = s. 

The Limit of Elasticity is the limiting stress beyond 
which the strain increases more rapidly than the stress. The 
limit is not perfectly definite, and can be determined approxi- 
mately only. A load greater than the elastic limit will pro- 
duce an appreciable permanent elongation after the load is 
removed. A stress less than the elastic limit will produce 
only a slight permanent elongation; such elongation may be 
inappreciable. 

Stretch Limit. — The stress at which the scale-beam of a 
testing-machine will fall while the straining-head is at rest is 
called the stretch limit. 

Ultimate Strength. — The maximum stress that a piece 
will endure in a testing-machine is called the ultimate strength 
of the material. The strength depends somewhat on the rate 
of testing. The more rapidly the testing proceeds the higher 
will be the apparent strength. It is desirable that some 
standard rate of testing may be adopted by engineers so that 
results may be strictly comparable. 

The Modulus of Elasticity is the result obtained by 
dividing the stress by the strain. If the stress is/ pounds 



STRENGTH OF BOILERS. 175 

per square inch and the strain is s per inch, then the modulus 
of elasticity is 

E = t 

S 

Reduction of Area. — The area of the test-piece of boiler- 
plate at the rupture is much less than that of the piece before 
testing. This reduction is important, as it shows the ductility 
of the metal, and its ability to change shape without too 
much distress under the influence of unequal expansion of 
different members of a boiler. 

Ultimate Elongation. — After the test-piece is broken the 
two parts are laid down in a straight line with the broken 
ends in contact, and the length of the distance between the 
points of attachments of the measuring clamps is measured. 
The ratio of the elongation to the original length (eight 
inches) is called the ultimate elongation. The ultimate elon- 
gation is generally given in per cent. This is important, for 
the same reason given for the contraction of area. 

Compression. — The preceding definitions are given for 
tension only, for sake of simplicity and brevity; they may 
be applied to pieces in direct compression if the term stretch 
or elongation is replaced by compression. 

Shearing. — Stresses have thus far been considered to be 
at right angles to the sections of the pieces to which they are 
applied, and produce either tension or compression at that 
section. A stress that is not at right angles to a section will 
tend to produce sliding at that section. A stress that is 
parallel to a section will tend to produce sliding only, and is 
called a shearing-stress. If a shearing-stress is uniformly dis- 
tributed, its intensity may be found by dividing the total force 
or load by the area of the section. 

The rivets of a riveted seam are subjected to a shearing- 
stress. 



1 76 S TEA M-B OILERS. 

Steel. — At the present time boiler-plates are made of 
mild, open-hearth steel; good wrought-iron plates can be 
obtained with some difficulty and trouble. Such steel is in 
reality a tongh, ductile, ingot iron, containing about one 
fourth of one per cent of carbon; it is nearly free from sulphur 
and phosphorus. The former impurity makes iron hot-short 
and the latter makes it cold-short, i.e., brittle when hot or 
cold. Plates of this material can be obtained of all sizes and 
thicknesses up to eight feet wide and an inch and a quarter 
thick. There is no limit to length except convenience of 
handling. 

Steel plate lor boiler-making should have the following 
properties: 

Tensile strength 55,000 to 60,000 

Elastic limit 30,000 to 33,000 

Elongation in eight inches.... 25 per cent or more 

Reduction of area at fracture. . 50 per cent or more. 

The plate should be free from blisters, lamination, or 
blow-holes. 

A piece cut from a plate less than three fourths of an inch 
thick should endure bending double under a heavy hammer, 
both hot and cold, without showing cracks. Heavy plates 
should endure bending at a small radius to a large angle with- 
out cracking. 

The upper end of the ingot into which the molten steel 
from the open-hearth furnace is cast, is liable to be affected 
by bubbles and other imperfections when the ingot is poured 
from the top. Such imperfections, if they are not removed, 
give rise to lamination in the plates, and therefore when the 
ingot is roiled into blooms the crop end should be cut long 
enough to remove all the bubbles. There is always a ten- 
dency, on account of the reduction of prices through com- 
petition, to reduce the length of the crop end, and conse- 



STRENGTH OF BOILERS. 1/7 

quently steel plates, though having the other required 
physical properties, are liable to show lamination. To guard 
against this, test-pieces should be cut from the ends of plates 
and tested in a testing-machine, and also by bending hot 
and cold. Ingots have been cast from the bottom, in which 
case bubbles are likely to be distributed throughout the 
ingot. 

Steel plates are sometimes classified as shell-plates and 
fire-box plates; the latter are supposed to be of special quality 
to endure the flanging required in the forming of the locomo- 
tive fire-box, and to endure the stresses in service due to the 
action of the fire, draughts of air entering through the fire- 
door, and from the unequal expansion of the fire-box and the 
parts of the shell to which it is stayed or otherwise connected. 
There does not appear to be any difference in the chemical 
and physical characteristics of these two grades, except the 
somewhat greater ductility of the fire-box plates, due to 
greater care in making. 

Angle-irons, T irons, bars, and rods used for staying and 
fastening boilers may be made of steel if welding is not re- 
quired in forming them. 

Blue Heat. — Steel plates, and other forms of mild steel, 
become brittle at a temperature corresponding, roughly, to a 
blue heat. A plate that will endure bending double, both 
hot and cold, is liable to show cracks if bent at a blue heat. 
In bending, flanging, and forging no work should be done on 
steel at a blue heat; properly, such work should be done at 
a bright red heat; work should never be continued after the 
steel becomes black. After the steel is cold it may be bent 
as readily as iron at the same temperature. 

Wrought Iron. — All the stays and fastenings of boilers 
that are made by welding should be made of tough, ductile 
wrought iron. Welds made by a skilful smith may have as 
great a strength as the bar from which they are made. A 
ductile bar may break in the clear bar instead of in the weld, 



178 S TEA M-B OILERS. 

on account of the hardening due to the work done on the bar 
at the weld. It is customary to assume that 25 to 50 per 
cent of the strength of the bar may be lost by welding. 

Wrought-iron plates of a quality suitable for boiler-making 
are now more expensive than mild-steel plates, which are in 
every way as well adapted to the purpose, and which have a 
higher strength. Consequently we find wrought-iron plates 
used only when specially demanded. Wrought iron does not 
show cracks when worked at a blue heat, and in general may 
endure more abuse in working. This caused wrought iron 
to be preferred by many after reliable steel was produced 
cheaply, but boiler-makers now understand the working of 
steel plates and avoid improper handling. 

Wrought-iron plates should show a limit of elasticity of 
23,000 pounds, and a tensile strength of 45,000 pounds to 
the square inch. 

Wrought-iron rods and bolts should have a strength of 
48,000 pounds per square inch. 

Rivets. — The rivets used in boiler-making are either iron, 
or steel similar in quality to steel used for boiler-plates. 

A rivet should bend cold around a bar of the same 
diameter, and it should bend double when hot without frac- 
ture. The tail should admit of being hammered down when 
hot till it forms a disk 2-J- times the diameter of the shank, 
without cracking. The shank should admit of being ham- 
mered flat when cold, and then punched with a hole equal in 
diameter to that of the shank, without cracking. 

The rods from which rivets are made should show a tensile 
strength of about 55,000 pounds for steel and about 48,000 
pounds for wrought iron. The other properties, such as 
ultimate elongation and contraction of area, should be like 
those for boiler-plate. 

The shearing strength of steel rivets is about 45,000 
pounds, and of iron rivets about 38,000 pounds; that is, the 



STRENGTH OF BOILERS. 1 79 

shearing strength will be about two thirds of the tensile 
strength. 

Cast Iron in different forms will show a tensile strength 
of 12,000 to 20,000 pounds to the square inch. Gun-iron, 
which is cast iron made with special care and skill from 
selected stock, has shown a tensile strength of nearly 30,000 
pounds to the square inch. In compression the strength of 
small pieces may be as high as 80,000 pounds to the square 
inch, but larger pieces, like columns, fail at 30,000 pounds 
to the square inch. 

Cast iron is used for some or all of the parts of sectional 
boilers, and for fittings such as manholes, though wrought 
iron is preferable for such purposes. Flat plates at the ends 
of cylindrical boilers are sometimes made of cast iron. 

In general, cast iron should never be used when it is sub- 
jected to severe changes of temperature or to stresses from 
unequal expansion, and should be replaced by wrought iron 
or mild steel whenever it is practicable. 

Couplings, elbows, and other pipe-fittings are made of 
cast iron. The brittleness is a convenience when changes are 
to be made, as joints that cannot be opened are readily 
broken. 

Malleable Iron, which is cast iron toughened by being 
deprived of part of the carbon, is used for pipe-fittings and for 
fittings of steam-boilers. It is used in place of cast iron for 
sectional boilers and for parts of water-tube boilers. Though 
tougher than cast iron, and though it will endure forging to 
some extent, its variability in quality and its unreliability 
prevent much reduction in weight and size when substituted 
for cast iron. 

Copper is largely used in Europe for making fire-boxes of 
locomotive-boilers and torpedo-boat boilers. Its greater cost 
is in part offset by the value of the scrap copper after the 
fire-box is worn out. 

Copper for fire-boxes, rivets, and stays should have a ten- 



T SO S TEAM-BOILERS. 

sile strength of 34,000 pounds to the square inch, and should 
show an elongation of 20 to 25 per cent in 8 inches. It should 
not contain more than one-half per cent of impurities. The 
greater ductility of copper, and its greater thermal conduc- 
tivity, permitting of greater thickness for furnace-plates, 
recommends it to European engineers. 

Copper is largely used on steamships for making piping of 
all sorts, such as steam-pipes and water-pipes. Such pipes 
are made of sheet copper, rolled up or hammered to shape, 
scarfed and brazed at the edges. The pipe is also brazed to 
brass flanges for coupling lengths of pipe, or for joining to 
steam-chests or other parts of the engine or boiler. If the 
brazing is not done with care and skill the brazed joint may 
lose as much as half the strength of the sheet copper. Several 
disastrous explosions of such piping have occurred. Conse- 
quently wrought-iron piping is finding favor for high-pressure 
steam. 

Bronze and Composition. Brass.— Bronze is properly 
an alloy of copper and tin; thus gun-metal is 90 parts of 
copper to 10 of tin. Compositions of various qualities are 
made of copper and zinc with more or less tin. Brass is an 
alloy of copper and zinc; for example, brass smoke-tubes are 
made of 70 parts of copper to 30 parts of zinc. Lead is 
added to brass and to composition to reduce the cost and to 
make the metal work easier. It may be considered as an 
adulteration, as it cheapens the metal at the expense of the 
quality. There are many special bronzes, such as phosphor- 
bronze and aluminium-bronze, which are used for 'special 
purposes. 

Brass is used to some extent for smoke-tubes of locomo- 
tive and other boilers, on account of its greater thermal con- 
ductivity, by European engineers. In America, brass is used 
for valves, gauges, and other boiler fittings. Composition or 
bronze is advantageously used for the valves and seats of 
safety-valves and wherever the service endured is excep- 



STRENGTH OF BOILERS. ' l8l 

tionally hard. Brass is more commonly used because it is 
cheaper. In a general way it may be said that the cost and 
quality of brass and composition is proportional to the copper 
it contains; thus red brass is better and costs more than 
yellow brass. Many small brass fittings on the market are 
sold at a price which precludes the use of proper alloys, and 
they are consequently soft and worthless. 

Stay-bolts are usually arranged in equidistant horizontal 
and vertical rows; as an example we may take the stay-bolts 
in the locomotive fire-box on Plate II. These bolts are 7/8 
of an inch in diameter outside of the threads, and are spaced 
4 inches on centres. The total load on each stay-bolt with 
a steam-pressure of 170 pounds to the square inch is 

4 X 4 X 170 = 2720 pounds. 

The diameter of the bolt at the bottom of the screw-thread 
is about 0.7 of an inch, and the area of the section is about 
0.4 of a square inch. The stress is consequently 

2720 -f- 0.4 = 6800. 

Sometimes the area is calculated from the external diam- 
eter of the bolt, a proceeding which may lead to a gross error. 
In the present instance the corresponding area is about 0.6 
of a square inch, which gives an apparent stress of about 
4500. 

Suppose that the thread is turned off from the body of 
the bolt, and that the diameter is thereby reduced to 5/8 of 
an inch. The area of the section is then about 0.3 of an 
inch, and the stress is 

2720 -f- 0.3 = 9000 +. 

The stress on stay-bolts should always be low to allow 
for wasting from corrosion, and to allow for unknown addi- 
tional stresses that may be caused by the unequal expansion 
of the plates that are tied together by the stay-bolts. 



182 



STEAM-BOILERS. 



Stay-rods. — Through-stays like those passing through the 
steam-space of the marine boiler, shown by Fig. 13, page 17, 
are treated much like stay-bolts. Thus the stays in question 
are 14 inches apart horizontally and 13 inches apart vertically. 
If they are each assumed to support a rectangular area 13 
inches wide and 14 inches long, the total force from 160 
pounds steam-pressure will be 

14 X 13 X 160 = 29120. 

The diameter of these stays in the body is 2 inches, which 
gives an area of section of 3.14 square inches. The stress is 
consequently 

29120 -\- 3.14 = 9300 

These stay-rods have swaged heads on which the screw- 
thread is cut, so that the diameter at the bottom of the 
thread is greater than the diameter of the body. 

Stay-rods which are used in connection with girders, as on 
Plate I, will have to carry loads which depend on the surface 
supported, the steam-pressure, and the number and arrange- 
ment of the stays. The determination of the load may be 
difficult and uncertain, but the calculation of the stress for a 
given load is very simple. 

Diagonal Stays. — If a stay-rod runs diagonally from a 
flat plate to the shell of a boiler, it will evidently be subjected 




Fig. 71. 
to a greater stress than it would be if it were a through-stay. 
Thus in Fig. 71 we have at the point a the parallelogram of 



STRENGTH OF BOILERS. 1 83 

forces abcd\ ab is the total pressure supported by the stay, ac 
is the pull on the stay, and ad is a force that must be taken 
up by the flat plate. But the triangles abc and aef are simi- 
lar, so that we have 



ac 



af Yae + ef 



ab ef ef 

Suppose, for example, that ae is two feet and ef is six 
feet ; then 




ac Vt -4- 6" 2 

^=-^- = I -° 54 ' 

or the pull on the stay is more than five per cent in excess of 
what a through-stay would be required to support. 

Gusset-stays are open to the defect that the distribu- 
tion of stress on the plate forming the stay is uneven and 
uncertain. It is customary to calculate them on the assump- 
tion that the resultant stress acts along 
a medial line, and is evenly distributed 
over a section at right angles to that line. 
A low apparent working-stress should be 
used. \ / 

Thin Hollow Cylinder. — Let Fig. \ 

72 .represent a semicircular steam-drum v ^~- — -'^ 

closed at the bottom by a thick flat plate. FlG * 72 * 

If the steam-pressure is/ pounds per square inch, the radius 

is r t and the length is /, then the pressure on the plate is 

2prl. 

If the thickness of the cylinder is /, and the stress per 
square inch on the metal of the cylinder is s, then the pull of 
the cylinder at one end of the plate is 

stl. 



1 84 S TEA M-BOILERS. 

But this must be equal to half the pressure on the plate, 
so that 

stl — prl. 

pr 

For safety the stress should not exceed the safe working 
stress for the material of which the cylinder is made; so that 
we have 

It is evident that the pull on the side of the cylinder and 
the stress per square inch will be the same if another half- 
cylinder is substituted for this plate, making a complete thin 
hollow cylinder. 

Example I. — A thin hollow cylinder five feet in diameter 
and half an inch thick, working at a pressure of 200 pounds, 
will be subjected to a stress of 

5 X 12 
200 X '- $ = 12,000 

pounds per square inch. If the cylinder is made of one con- 
tinuous plate of steel without longitudinal joint, this stress 
will be about one fifth of the ultimate strength. 

Example 2. — If it is desired that the stress shall be 9000 
pounds in a cylinder 9 feet in diameter when exposed to a 
pressure of 120 pounds to the square inch, then the thickness 
of the plate should be 

pr 9 X 12 

t — — : = 120 X -5- 9000 = O.72 

of an inch. 

End Tension on a Cylinder. — In the preceding cylinder 
we have considered the tension on a section at the side of the 



STRENGTH OF BOILERS. I 85 

•cylinder. Let us now consider the tension on a transverse 
section. 

If the cylinder is closed by a flat plate at the end, the 
area of that plate will be 

3.1416?- 2 , 

and the total force due to a pressure of p pounds per square 
inch will be 

3.i4i6r>. 

This force will be resisted by a ring of metal having a cir- 
cumference 2 X 3.1416?-, and a thickness t. The resistance 
of the ring will be 

2 X 3.14167-/5, 

representing the stress by s. Consequently we shall have 

2 X 3.1416^ = 3.1416^/. 

pr 

It is evident that the stress from the end pull is half the 
stress on the section at the side of a cylinder, and conse- 
quently a cylinder made of homogeneous material without 
joints will always be ruptured longitudinally. 

It is also evident that the stress from the end pull will be 
the same if the end of the cylinder is closed by a spherical 
surface, or by any other figure, instead of a flat plate. 

Thin Hollow Sphere- — A section taken through the cen- 
tre of a sphere is in the same condition as a transverse sec- 
tion of a thin cylinder, and will be subjected to the same 
stress, if the sphere has the same thickness and is subjected 
to the same internal pressure. 

Formerly the ends of plain cylindrical boilers were made 
hemispherical, but such ends are difficult to make and are 
needlessly strong if of the same thickness as the cylindrical 



1 86 



5 TEA M-B OILERS. 



shell. It is now the practice to curve such ends to a less 
radius than that of the cylindrical shell. If the radius of the 
head is equal to the diameter of the shell, then with the same 
thickness of plate the stress will be the same per square inch, 
provided there are no seams in head or shell. The heads 
usually do not have a seam, and the shells always have a 
seam; the margin of strength in the head, when the same 
thickness of plate is used, under this condition may be offset 
against the possible injury done to the head in shaping it. 

The construction known as a bumpcd-up head has the 
edge flanged into a cylindrical form to make a joint with the 
shell, and to avoid the awkward stress that would be thrown 
onto the cylindrical shell if the true cylindrical and spherical 
surfaces were allowed to intersect. 

If it is inconvenient to curve the head to a radius as small 

as the diameter of the cylinder, then a thicker 

plate may be used, with a longer radius. 

Rivets. — The plates of a boiler are joined at 

the edges by rivets; rivets are also used in stays 

and other members. 

LThe usual form of rivets is shown by Fig. 
73. If the diameter of the rivet is D, then the 
Fig. 73. proportions may be 



^S 



A 

5=1-4; 



B 
D 



= 0.7; 



D = 3/4. 



STRENGTH OF BOILERS. 



187 



The length of the rivet will depend on the number and 
thickness of the plates through which it is to pass. 

The rivet represented by Fig. 73 has a pan head. Of the 
rivets shown by Fig. 74, A, B, and C have pan heads, and D 
and E have round or hemispherical heads. 

The form of the point of a rivet will depend on the way 
in which the rivet is driven and on the shape of the tools or 
dies used for forming the point. The rivet A has a straight 

ABC 




conical point; this is the only form that can be made when 
the rivet is driven by hand with flat-faced hammers. 

The rivet B has the head formed by a die or snap. The 
rivet is driven by a few heavy blows of a hammer, and the 
head is roughly formed; then a die or snap is placed on the 
point and driven to form the point by a sledge-hammer. 

C shows a rounded conical point commonly used for 
machine-driven rivets. The heads of such rivets may have a 
similar form. 

D represents the usual form of countersunk rivets: the 
hemispherical head is not a peculiarity of such rivets; it is 
occasionally used with any form of point. The rivet E has 
some fulness or projection at the point beyond the counter- 
sink. 

After a rivet is driven, both ends are called heads; the 
distinction of heads and points is made here for convenience 
in description. 

The straight conical form A is liable to be too flat and 
weak. Its height should be three-fourths the diameter of 
the rivet. 



1 88 STEAM-BOILERS. 

When rivet-holes are punched in plates they are slightly 
conical, as shown by B, Fig. 74, which shows the two smaller 
ends of the rivet-holes placed together to facilitate the proper 
filling of the hole by the rivets. The other rivet-holes are 
straight, as they would be if drilled. 

Riveted Joints. — The proportions of riveted joints, such 
as diameter and pitch of rivets, are determined in part by 
practice and in part by a method of calculation to be explained 
later. In practice it is found necessary to limit the pitch of 
the rivets, and consequently the diameter, to be used with a 
given thickness of plate, in order that the joint may be made 
tight by calking. This limitation frequently makes the joint 
weaker than it otherwise would be. 

The edges of plates are either lapped over and riveted, or 
brought edge to edge and then joined by a cover-plate which 
is riveted to each of the two plates. The first method makes 
a lap-joint and the second a butt-joint. 

Fig. 75 shows a single-riveted lap-joint and Figs. y6 and 
yy show double-riveted lap-joints. The rivets in Fig. 76 are 
said to be staggered; the form shown by Fig. yy is called 
chain-riveting. 

Butt-joints with two cover-plates are shown by Figs. 80 
and 81. The outer cover-plate is narrow, with rivets placed 
close enough together to provide for sound calking. The 
inner plate is wider, and as its edges are not calked they may 
have a row of more widely spaced rivets. These joints, and 
those shown by Figs. 78 and 79, are designed with the view 
securing more strength than can be had with a plain lap-joint 
like Fig. y6, or than can be had with a butt-joint with cover- 
plates of equal width. 

Efficiency of a Riveted Joint. — The strength of a riveted 
joint is always less than that of the solid plate, because some 
of the plate is cut away by the rivets. This is very evident 
in the case of a single-riveted joint, such as that shown by 
Fig. 75 ; it will be found to be true for more complicated 
joints, such as those shown by Figs. 80 and 81. The efficiency 



STRENGTH OF BOILERS. 1 89 

of a riveted joint is the ratio of the strength of the joint to 
the strength of the solid plate. 

The strength and efficiency of a given riveted joint can be 
properly determined only by direct test on full-sized speci- 
mens, which have considerable width. Tests on narrow 
specimens are liable to be misleading. Tests on boiler-joints 
are expensive, and can be made only on large and power- 
ful testing-machines. Tests have been made on behalf of 
the United States Navy Department at the Watertown 
Arsenal on a large number of single-riveted joints, on a con- 
siderable number of double-riveted joints, and on a few 
special joints. A few tests have been made elsewhere on full- 
sized joints. These tests give us important information that 
can be used in designing joints for boilers, but we cannot in 
general select a joint directly from the tests. 

Methods of Failure. — A riveted joint may fail in one of 
several methods, depending on the proportions, such as thick- 
ness of plate and the diameter and pitch of the rivets. This 
can be clearly seen in case of a single-riveted joint like that 
shown by Fig. 75. Such a joint may fail: 

(1) By tearing the plate at the reduced section between the 
rivets. If the rivets have the diameter d and the pitch /, 
then the ratio of the area of the reduced section to that of 
the whole plate is 

- d 

P ' 

(2) By shearing the rivets. 

(3) By crushing the plate or the rivets at the surface where 
they are in contact. 

(4) By cracking the plate between the rivet-hole and the 
edge of the plate, or by some method of failure due to in- 
sufficient lap. A riveted joint never fails by this method in 
practice, because the lap can always be made sufficient. 

The failure of more complicated joints may occur in 
various methods, which will be considered in connection with 
the calculation of some special joints. 



igo STEAM-BOILERS. 

Drilled or Punched Plates. — In the better class of boiler- 
shops it is now the practice to drill rivet-holes in plates after 
the plates are in place, so that the holes are sure to be fair. 
Sometimes the holes are punched to a smaller diameter and 
then drilled out to the final size after the plates are in place. 
The result is the same as though the holes were drilled in the 
first place, as the metal near the hole, which was injured in 
punching, is all removed. The metal remaining between 
drilled holes does not have its properties changed by the 
drilling. On the contrary, the metal between punched holes 
is always injured more or less. In general, soft ductile metal 
is injured less than hard metal, and further, soft-steel plates 
are injured less than wrought-iron plates. 

When boiler-plates are punched and then rolled to form 
cylindrical shells, some of the holes are liable to come unfair, 
so that a rivet cannot be passed through. In such cases the 
holes should be drilled to a larger size, and a rivet of corre- 
sponding diameter should be substituted. Careless or reck- 
less workmen sometimes drive in a drift-pin, and stretch or 
distort the unfair holes so that a rivet can be forced through. 
The plate is liable to be severely injured by such treatment, 
and the rivet cannot properly fill the rivet-holes. Unfortu- 
nately it is difficult or impossible to detect bad work of this 
kind after the rivets are driven. 

Tearing". — The metal between the rivet-holes in a riveted 
joint cannot stretch as a proper test-piece does in the testing- 
machine, and consequently it shows a greater tensile strength 
than a test-piece from the same plate. Some tests on single 
or double riveted joints with small pitches show an excess 
of strength from this cause, amounting to ten per cent or 
more. The excess appears to be uncertain and irregular, so 
that if any allowance is made for it, it should be by a skilled 
designer after a careful, study of all the tests that have been 
made. Ordinarily it will be safer to use the tensile strength 
shown by test-pieces in the testing-machine, especially for joints 
like Fig. 78, which have a large pitch for some of the rivets. 



STRENGTH OF BOILERS. 1QI 

Shearing. — In general it is fair to assume the shearing 
strength of rivets of iron or steel to be two thirds the tensile 
strength of the metal from which the rivets are made. 

Crushing. — It is customary to assume that the pull on a 
riveted joint is evenly distributed among the rivets in the 
joint, and to divide the total pull by the number of rivets to 
find the shearing or crushing force acting on one rivet. It is 
further customary to assume that the intensity of the crushing 
force on the surface where the rivet bears on the plate, may 
be found by dividing the total force on one rivet, by the 
product of the diameter of a rivet and the thickness of the 
plate. 

The crushing-stress on rivets in joints that fail by crushing 
is found by experiment to be high and irregular. In some 
cases it has amounted to 150,000 pounds per square inch; in 
a few tests it is less than 85,000 pounds. It is probable that 
95,000 pounds may be used with safety in calculating riveted 
joints for boilers. Now the stress on the bearing-surface 
will seldom be so much as one third the ultimate strength, 
even during a hydraulic test of a boiler, and it is not probable 
that a joint will be injured in this way unless the stress 
approaches the ultimate strength. 

Friction of Riveted Joints. — It is evident that there must 
be considerable friction between plates that are firmly clamped 
together by rivets driven hot. It has been proposed to take 
some account of this friction in calculating riveted joints, or 
even to allow the friction to be the determining element in 
proportioning riveted joints. Such a method is shown by 
experiment to be unsafe, for slipping takes place at all loads, 
beginning at loads that are much smaller than a safe load, and 
the effect of friction disappears before a breaking load is 
reached. 

Lap. — The distance from the centre of the rivet-hole to 
the edge of the plate is called the lap. The lap is usually 
once and a half the diameter of the rivet, a proportion that 
appears to be satisfactory. 



192 



S TEA M-B OILERS. 



Diameter of Rivet. — The minimum diameter of punched 
holes is determined by the consideration that the punch 
should not be broken. In the ordinary methods of punching 
boiler-plates the diameter of the punch should at least be as 
much as the thickness of the plate. It very commonly is 
once and a half the thickness of the plate. 

Drilled rivet-holes may have any diameter. They never 
have a diameter less than the thickness of the plate. The 
maximum diameter of rivet to be used with any kind of 
riveted joint will in general be determined by the considera- 
tion that the tendency to crush the plate in front of th-e rivet 
should not be greater than the shearing strength of the rivet. 
The maximum diameter thus found is liable to give too large 
a pitch. 

Pitch. — The maximum pitch for a given plate along a 
calked edge should be determined by the consideration that 
the plate should be held up rigidly enough to make a tight 
joint without excessive calking. The pitch of rivets, like 
those in the outer row of the joint shown by Fig. 78, need 
not be governed by this rule. There does not appear to be 
any explicit rule deduced either from practice or experiment 
for determining the proper pitch of rivets. 

Single-riveted Lap-joint. — In the joint shown by Fig. 75 
let the thickness of the plate be /, the 
diameter of the rivet d> and the pitch 
p, all in inches. Let the tearing 
strength of the plate be f t = 55,000, 
the shearing strength be f s = 45,000, 
and the resistance to crushing be 
f c — 95,ooo, all for mild steel. 
Assume the proportions 

</= 15/16, /=7/i6, p = 2i, 

It will be sufficient to consider a portion of the plate 
having a width equal to the lap. The failure of such a strip 
may occur in one of three ways : 



]._._! 


]i 


p6o 




1 



Fig. 75. 



STRENGTH OF BOILERS. 1 93 

1st. Shearing one rivet. The area to be sheared is — 

4 

1 T A T fS// a 

or — . The resistance to shearing is found by multi- 
plying this area by the shearing strength of the rivet: 

nd* n X 15 X 15 X 45.000 

T~ /s== ^Ti6^T6 =35,340. 

2d. Tearing plate between rivets. The effective width of 
the strip under consideration, allowing for the rivet-hole, is 
p — d, and the thickness of the plate is t\ the resistance to 
tearing is 

(P - d)tf = (2} - i*) T \ x 55,ooo = 31,580. 

3d. Cru siting of rivet or plate, The conventional method 
is to assume the effective bearing area to be equivalent to the 
diameter of the rivet multiplied by the thickness of the plate. 
The resistance is considered to be 

dt fc — U X -A X 95,ooo = 38,970. 

The strength of a strip of the plate 2\ inches wide is 

2i X T \ X 55,ooo= 54,140. 

The calculated resistance to tearing is less than the 
resistance to shearing or compression. The apparent effi- 
ciency of the joint is 

3 J ,58o 

100 X - — = 58.3 per cent. 

54,140 D ^ 

If it De assumed that the resistance to tearing of the 
section between rivets will have an excess of ten per cent 
over the resistance of a piece in a testing-machine, then the 
resistance to tearing between rivets will appear to be 34,740. 
This figure is not far from the resistance to shearing, though 
still inferior. If it be further assumed that the whole plate 



i 9 4 



S TEA M-B OILERS. 



outside of the joint will show a tearing strength of only 
55,000 pounds per square inch, the efficiency of the joint will 
appear to be more than five per cent greater than that given 
above. It is probably wise to ignore the excess of strength 
due to the fact that the plate between the rivets will not 
draw down for reasons that have already been stated at length. 
Double-riveted Lap-joint. — The rivets in this joint may 
be staggered as shown by Fig. 76, or chain-riveting may be 





Fig. 76. 

used as in Fig. JJ. If the rivets are staggered and the two 
rows are too near together, it is possible that the plate may 




Fig. 77. 



tear down from a rivet in one row to the nearest rivet in the 
next row, and thus have, after tearing, a jagged edge. With 
the usual proportions such a failure will not occur, but the 
plate will tear between rivets in the same row, if it fails by 



STRENGTH OF BOILERS. 1 95 

tearing. The calculation for efficiency will consequently be 
the same for both methods of riveting. 

Let the dimensions be 

t = 7/16, d = 13/16, p = 2\. 

The joint may fail in one of three ways : 

1st. Shearing two rivets. The assumed strip having a 
width equal to the pitch will be held by two rivets ; this is 
apparent at once for chain-riveting. For staggered rivets 
such a strip will contain one whole rivet and half of two 
others, so that the same rule holds. The resistance of two 
rivets to shearing will be 

2 7td 2 . - -. 
/, = 46,660. 

4 
2d. Tearing between two rivets. The resistance is 

(/ — d)tf t = 40,600 

3d. Crushing in front of rivets. Just as for shearing, we 
have here the resistance at two rivets equal to 

2dtf c — 67,540. 

The strength of the plate for a width of the pitch is 

ptf t — 60, 160. 

The plate will apparently fail by tearing, and the effi- 
ciency of the joint will be 

40,600 - 
100 X 5— L - -r- — 67.5 per cent. 
60,160 

The increase of efficiency of the double-riveted lap-joint 
over the single-riveted joint is clearly due to reducing the 
diameter of the rivet and increasing the pitch. A further 
increase of efficiency could be obtained by using three rows of 
rivets; this, however, is practicable only for thick plates, as 
we are liable to get too wide a pitch for sound calking. 

Single-riveted Lap-joint, Inside Cover-plate In this 

joint the plates are lapped and joined by a single row of rivets; 



196 



S TEA M-BOILERS. 



and a plate is worked inside and riveted through the sheil 
with a single row of rivets, which are spaced twice as far apart 
as the rivets in the lap. In making up the joint all three rows 
of rivets may be driven at the same time. The lapped joint 
only is calked ; the pitch of rivets through the lap must con- 
sequently be small enough to give sound calking. The outer 
rows of rivets are not controlled by this rule. 

.We will here consider a strip having the width a, Fig. 78, 
equal to twice the pitch of the rivets in the lap. Such a strip 
will be held by two rivets in the lap and by one rivet in an 
outer row. 

Assume the following dimensions : 

Thickness of shell and of cover-plate, t — S/ 1 ^- 

Diameter of rivets (iron), d — 3/4. 

Pitch of rivets in lap, / = if. 

Pitch of outer rows of rivets, P— 3 J. 

Shearing resistance of iron rivets per square inch or f s = 
38,000 lbs. 

The joint may fail in one of five ways: 



\ 


/ 1 


> © 


ooc 


)©cj)©p 






, p , 


© c 


\-a—f 


) © 


1 l 


j 



Fig. 78. 
1st. Tearing between outer row of rivets. The resistance is 
(P~d)tf t = 47,270. 



STRENGTH OF BOILERS. 1 97 

2d. Tearing between inner row of rivets, and shearing 
outer row of rivets. The resistance is 

(P-2d)tf+~f s = 51,150. 

4 

Since the rivets are iron, f = 38,000. 

3d. Shearing three rivets. The resistance is 

4 

4th. Crushing in front of three rivets. The resistance is 

ltdf e — 66,800. 

5 th. Tearing at inner row of rivets and crushing in front 
of one rivet in outer roiv. The resistance is 

(P-2d)/ t + td/ c = 56,641. 

The strength of a strip of plate 3J inches wide is 

Itf t = 60,160. 

The least resistance is offered by the first method, giving 
for the efficiency 

47,270 
100 X 6o7T6o= 78.6 per cent. 

If the inside cover-plate is thinner than the shell, addi- 
tional complication will be introduced into the calculations 
for resistance. 

Double-riveted Lap-joint with Inside Cover-plate. — 
The arrangement of this joint is shown by Fig. 79. Assume 
the dimensions: 

Thickness of shell and of cover-plate, / = 7/16. 

Diameter of rivets (steel), d = 13/16. 

Pitch of rivets in lap, 2 T 5 f . 

Pitch of outer rows of rivets, P= 4|. 



I98 STEAM-BOILERS. 

The methods of failure are: 
1st. Tearing at outer row of rivets. 

Resistance (P — d)tf t — 91,740. 
2d. Shearing four rivets. 

Resistance f s = 93,310. 



I 




{ 


)-k 


b © © 


©A©X©-©_©_ 
© ®*© © © 


p ■ 


> c 


^ph© © 


1 





Fig. 79. 

3d. Tearing at inner row and shearing outer row of rivets. 
A strip having the width of the pitch of the outer row of 
rivets will be weakened at the rivets in the lap to the extent 
of one rivet-hole and half another rivet-hole. The resist- 



ance is 



Ttd' 



(P-i i d)tf + --f s = 105,285. 



4th. Crushing in front of four rivets. 

Resistance 4tdf = 135,080. 

5 th. Tearing at inner row of rivets and crushing in front 
of one rivet. 

Resistance (P - \\d)tf + tdf = 115,730. 



STRENGTH OF BOILERS. 199 

Strength of strip 4$ inches wide, 

Ptf t = 111,290. 

9 1 1 74° 
Efficiency = 100 X T T T „ „ = 82.4 per cent. 
J 11 1,290 ^ v 

Double-riveted Butt-joint. — The joint shown by Fig. 
80 has a cover-plate inside and another, narrower, outside. 
There are two rows of rivets on each side of the joint. The 
inner rows are nearer together and pass through both cover- 
plates. 




Fig. 80. 

The outer row of rivets are wider apart and pass through 
the inner cover-plate only. 

The dimensions assumed are: 

Thickness of the plate and of both cover-plates, t = 7/16. 

Diameter of rivets (iron), 15/16 inch. 

Pitch of inner row of rivets, 2f. 

Pitch of outer row of rivets, 5|. 

There are five ways in which the joint may fail : 
1st. Tearing at outer row of rivets. The resistance is 

(P-d)tf t = 103,770. 



200 STEAM-BOILERS. 

2d. Shearing tzvo rivets in double shear and one in single 
shear. If the plate pulls out from between the cover-plates 
shearing off the rivets, then the rivets in the inner row must 
be sheared through on both sides of the plate, or they are in 
double shear. The outer row of rivets are sheared at only one 
place. There are, consequently, five sections of rivets to be 
sheared for a strip as wide as the larger pitch. The resist- 
ance is 

— — f = 131,100. 

4 

3d. Tearing at inner row of rivets and shearing one of the 
outer row of rivets. The resistance is 

{P -2d)tf + n —f = 107,430. 

4th. Crushing in front of three rivets. The resistance is 

ltdf = 116,880. 

5 th. Crushing in front of tzvo rivets and shearing one 
rivet. The resistance is 

7fd* 

2tdf + -—f= 104,140. 
4 

The strength of a strip 5J inches wide is 

5iX T \ Xf t = 126,560. 

The efficiency is 

103,770 
100- — 7 — ^— = 82 per cent. 
126,560 r 

Triple-riveted Butt-joint. — The joint shown by Fig. 81 
has three rows of rivets on each side. Two rows pass through 
both cover-plates, and the third or outer row passes through 
the inner cover-plate only. 



STRENGTH OF BOILERS. 



201 



The dimensions are: 

Thickness of shell, / = 7/16. 
Thickness of both cover-plates, t c = 3/8. 
Diameter of rivets (steel), d = 15/16. 
Pitch, inner rows, p = 3§. 
Pitch, outer row, P= 7}. 




Fig. 81. 



The joint may fail in one of five ways : 

1st. Tearing at outer rozv of rivets. The resistance is 

(P-d)tf = 151,890. 

2d. Sliearing four rivets in double shear and 07ie in single 
shear. The resistance is 



gird 



fs= 279.450. 



3d. By tearing at middle row of rivets (ivhere the pitch is 
3| inches) and shearing one rivet. The resistance is 

nd* 
(P-2d)tf+ --f s = 160,340. 



202 STEAM-BOILERS. 

4th. By crushing in front of four rivets mid shearing 
one rivet. The resistance is 

nd' 1 
4dtf c +— /= 186,830. 

4 

5th. By crusJiing in front of five rivets. Four of these 
rivets pass through both cover-plates and will crush at the 
shell-plate. The fifth rivet passes through the inner cover- 
plate only, and will crush at that plate, since the cover-plates 
are thinner than the shell-plate. The resistance is 

4 dtf + dt c f c = 189,170. 

The strength of a strip of plate 7 J inches wide is 

Ptf= 174,370. 

The efficiency is 

151,890 

100 X — = 87 per cent. 

174,370 ^ 

Designing Riveted Joints. — One element of the design 
of a riveted joint is to secure as high an efficiency for the 
joint as is consistent with other requirements, such as a proper 
pitch for calking. 

A consideration of the example of a single-riveted lap- 
joint will show that the efficiency can be improved by increas- 
ing the diameter of the rivet and by increasing the pitch. In 
the first place, since the joint will fail by tearing between the 
rivets, simply increasing the pitch with the same size of rivet 
will give a greater efficiency. If the pitch is increased till 
the rivet fails, the failure will be by shearing. Now the 
resistance to crushing is represented by 

dtf ci 

while the resistance to shearing is represented by 

TteP 

4 /iJ 



STRENGTH OF BOILERS. 203 

that is, the resistance to crushing increases proportionally as 
the diameter, while the resistance to shearing increases as the 
square of the diameter. The shearing resistance increases the 
more rapidly, and can be made equal to the crushing resist- 
ance by using a larger rivet. Of course this will demand a 
further increase of pitch. 

In the case of the single-riveted lap-joint now under dis- 
cussion, the proper proportions for a joint that shall be equally 
strong against shearing, tearing, and crushing can be calculated 
directly. The usual way is to determine the diameter of the 
rivets by making them equally strong against shearing and 
crushing. Equating the expressions for crushing and shearing 
resistance, we have 

dtfc=—fn or d ~-f-< 

4 J,7t 

For the case in hand with steel plates 7/16 of an inch thick, 
and steel rivets, the diameter will be 

45,000 n " • /• 

Having the diameter of the rivets, we may now calculate 
the pitch by equating the shearing and tearing resistances, 
which gives 

ltd* , ~ , fs ltd* 

—fs = {p-d)tf t , or p= J -?- 7+dm 

4 Jt ¥ 

For the case in hand we have 



45,000 n 1. 17* 
'=55.ooo 4 X T V +I - I7 = 3 - 2 ' 



The efficiency of the joint is the ratio of the resistance to 



204 STEAM-BOILERS. 

tearing between the rivets to the strength of a strip of plate 
having a width equal to the pitch, so that the efficiency is 

flp-d)t ^ p-d 

fspt P ' 

In the case in hand the efficiency is 
i 3-2 - 1. 17 



100 3.2 



63.4 per cent. 



But the pitch calculated in this method is too great for 
proper calking with a plate of the given thickness. 

The double-riveted lap-joint has three possible ways of 
failure, which lead to two equations for finding the diameter 
and pitch of rivets. Equating the shearing and crushing 
resistance for two rivets, we have 

2—-f s = 2dtf ei or d = J ~ ^-^ 

4 Is n 

which will give the same size rivet for a plate of a given 
thickness as would be found for a single-riveted joint. Now 
this method has been found to lead to too large a rivet for a 
single-riveted joint, where a strip having a width equal to the 
pitch carries one rivet. In the double-riveted joint such a 
strip carries two rivets, and consequently it is the more cer- 
tain that the method proposed will give too large a rivet, and 
of course too large a pitch for proper calking. The advan- 
tage of double riveting is that smaller rivets may be used to 
provide the requisite shearing resistance, and the plate may 
be less cut away at the section between rivets. 

In designing a double-riveted lap-joint it is customary to 
assume a diameter for the rivets and then determine the pitch 
by equating the shearing resistance of two rivets to the tear- 
ing resistance between the rivets. If the resulting pitch is too 
large for proper calking, the diameter of the rivets must be 
reduced. If, on the contrary, the resulting pitch is less than 



STRENGTH OF BOILERS. 205 

may be allowed, a slightly larger diameter and pitch may be 
used. 

A design of a joint like the single-riveted lap-joint with 
inside cover-plate, which has a wide and a narrow pitch, 
involves some difficulty and complexity. The fundamental 
idea of such a joint is to make the resistance to tearing at the 
inner row of rivets (when the pitch is small) plus the shearing 
of the outer row of rivets greater than the resistance to tear- 
ing at the outer row of rivets (when the pitch is larger). To 
insure this condition we may proceed as follows: Equate the 
resistance to tearing at the outer row of rivets to the resist- 
ance to tearing at the inner row plus the resistance to shearing 
one rivet at the outer row. This gives 

(P - d)tf t = (/> - 2d)tf t + — /„ 

4 
whence 

The result is the minimum diameter of rivets allowable. 
We may now choose a slightly larger diameter of rivets, and 
then determine the pitch in three different ways, namely, by 
equating the resistance to tearing at the outer row of rivets, 
in succession, to the resistance to shearing of three rivets, 
to the resistance to crushing in front of three rivets, and 
to the resistance to tearing between the inner rows of rivets 
and compression before one rivet. The smallest pitch 
obtained will be the correct one to use with the given diam- 
eter of rivet. Should the efficiency of the joint be unsatis- 
factory, an attempt may be made to raise the efficiency by 
increasing the diameter of the rivets. 

Practical Considerations. — In proportioning a riveted 
joint, the following considerations, some of which have already 
been mentioned, must receive attention: 

The pitch of rivets near a calked edge must not be too 
great for proper caulking. 



/ 



206 S TEA M-B OILERS. 

Rivets must not be too near together for convenience in 
driving. 

Punched holes must have a diameter greater than the 
thickness of the plate. 

A riveted seam must contain a whole number of rivets. 
Again, it is desirable that similar seams, as for example the 
longitudinal seams for the several rings of a cylindrical boiler, 
shall have the same pitch. 

It is evident that the design of a boiler-joint cannot be 
considered apart from the general design of the boiler. 

Flues. — The tendency of internal pressure in a thin hol- 
low cylinder is to give it a true cylindrical shape; conse- 
quently, with fair workmanship, the formulae for thin hollow 
cylinders may be applied to the calculation of boiler-shells 
subjected to internal pressure. But the tendency of external 
pressure is to exaggerate any imperfection of shape, and 
cylindrical flues fail by collapsing. 

The pressure at which a flue will collapse can be found by 
direct experiment only. 

The earliest and for a long time the only tests on the 
collapsing of flues were those made by Fairbairn, and pub- 
lished in the Transactions of the Royal Society, in 1858. All 
of the tubes tested were 0.043 °f an mcn thick; they varied 
in diameter from 4 inches to 12 inches, and in length from 20 
inches to 60 inches. From these tests he deduced the em- 
pirical formula 

806,300 X / 2I9 



P 



/X d 



in which / is the length of the tube in feet and d and / are 
the diameter and thickness in inches, while/ is the collapsing 
pressure in pounds per square inch. Sometimes the exponent 
of / is made 2 instead of 2.19, for sake of simplicity. As /is 
commonly a proper fraction, the use of a smaller exponent 
will give a higher calculated collapsing pressure. 



STRENGTH OF BOILERS. 



20/ 



The tubes in this series were too small, and more especially 
too thin, to serve as a proper basis for the calculation of boiler- 
flues. It is quoted because it has been widely used, and is 
now used by some engineers. It sometimes gives a calculated 
pressure higher and sometimes lower than that at which flues 
will collapse, and its use is liable to lead to disappointment if 
not to disaster. 

The following table gives the results of some tests on 
larger boiler-flues, taken from Hutton's " Steam-boiler Con- 
struction." The table gives the dimensions and the actual 
collapsing pressure, and also the collapsing pressure by Fair- 
bairn's rule and by a rule proposed by Hutton. 

EXPERIMENTS ON THE COLLAPSING PRESSURE OF BOILER- 
FLUES. 



Where or by Whom Made. 



By Fairbairn 

By Fairbairn 

By Fairbairn 

By Fairbairn ... 

Engineering Dept., U. S. N. 

At Greenock 

By Knight 

By Knight 

By Kntght 

By J. Hovvden & Co., Glas- 
gow 



Di 


mensions. 




Collapsing Pressure in 
Pounds per Square Inch. 


Q-5 

— c 
rt— < 
5 c 

v z 


c 


Xi 

u 

c c 

<" c 

C — 

.* 

.a «» 


•° a 

C V 


irS 

re .b 


culuted by 
tton's Rule. 


X V 


v a 


js'O 


O X 




re 3 


W u 


J £ 


H fn 


feW 


Ufa 


UX 


2 


3 


4 


5 


6 


7 


7.87 


276 


5 


no 


log 


114 


33-5 


360 


11 


99 


Si 


113 


42 


420 


12 


97 


7S 


IOO 


42 


300 


12 


127 


10S 


ng 


54 


36 


8 


128 


3ii 


120 


38 


86 


16 


450 


740 


43b 


36 


24- 


8 


235 


700 


21S 


36 


24 


12 


468 


1568 


490 


36 


48 


12 


390 


784 


35o 


43 


23 


17 


840 


275S 


842 



On the whole the rule proposed by Hutton gives the most 
concordant results; in most cases Hutton's rule gives a cal- 
culated collapsing pressure that is smaller than the actual 
collapsing pressure; in no case is the calculated result very 
largely in excess. Fairbairn's rule in some cases shows a very 



208 STEAM-BOILERS. 

close agreement with experiment, but in others it shows a 
dangerous excess. 
Hutton's rule is 

Cf 

in which / is the length in inches, d is the diameter in inches, 
and t is the thickness in thirty-seconds of an inch. C is a con- 
stant which Hutton makes 600 for iron and 660 for steel. 

Mr. Michael Longridge, as a result of an investigation of 
many boiler-flues, most of which have endured service for 
years, but some of which failed, gives a rule in the same form 
but with a constant 540 instead of 600. 

For oval tubes and flues it is recommended that the above 
rules be applied, using for the diameter twice the maximum 
radius of curvature. 

Strengthened Flues. — It is clear from inspection of the 
preceding table of tests on boiler-flues that the collapsing 
pressure decreases as the length of the flue increases. Account 
is taken of this in Hutton's formula, by introducing the 
square root of the length into the denominator of the expres- 
sion for calculating the collapsing pressure of a flue. Stating 
the proposition in the converse manner, the reason why a 
short flue is the stronger is that the ends of the flue are kept 
in a circular form by the plates to which the flue is riveted. 

It has been customary to strengthen plain flues by the aid 
of rings placed at regular intervals. The section of a ring 
made of angle-iron is shown by Fig. %2a. The ring is riveted 
to the flue at intervals, a thimble being placed over each rivet 
to give space for circulation of water between the ring and 
the flue. The rings were sometimes solid, made of one piece 
of angle-iron bent up and welded. Most frequently the ring 
was in halves, which were merely belted together at the joint. 
Such rings could be easily removed when the flue was taken 
out of the boiler. 

A better method of strengthening a flue is to make it of 



STRENGTH OF BOILERS. 



209 



short pieces so joined at the ends as to make stiffening rings. 
Fig. 82 shows three ways in which this can be done. At b 
is shown the Adamson ring, formed by flanging the edges of 
the short lengths of flue outwardly, and riveting through a 
welded iron ring. At c is shown a welded ring of T iron, to 
which the short lengths can be riveted without flanging. This 





Fig. 82. 



method provides for calking both inside and outside. It 
does not require the flue to be flanged; but flanging by 
machinery is rapid, and does not give trouble when good iron 
or steel is used. Material that will not stand flanging should 
not be used for flues. At d is shown the bowling hoop-ring, 
which has the advantage that it provides for longitudinal 
expansion of the flue. 

Flues for Scotch and other marine boilers with furnace- 
flues, are stiffened by transverse or helical corrugations, which 
provide at the same time for longitudinal expansion. A 
number of methods of corrugating furnace-flues will be illus- 
trated in connection with tests given on the following pages. 

Tests on Furnace-flues. — The strength of corrugated and 
other stiffened flues can be determined only by tests on full- 
sized specimens. The following tests are taken from a paper 
by Mr. B. D. Morison, read before the Northeast Coast In- 
stitution of Engineers and Shipbuilders. 



2IO 



S TEA M-B OILERS. 



Furnaces made with Adamson Joints. 

Tests made at the Works of Hall, Russell & Co., Aberdeen, in 
1882, and of J. Howden & Co. in Glasgow, in 1887. 

"ii 11 11 11 ir 




Date 

of 
Test. 



I8S2 



1887 



Length 
Furnace. 



6 ft. 5! in. total 

length. 
Length of 

rings : 
18*". 19", 19", 

and 20" 



7 ft. •§• in. total 

length. 

Length of each 

ring, 23" 






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1" 






2 » 






2d ring 






1 5" 






3a » 
3d ring 


43 


9/64 


15'' 






32 ' 






4th ring 






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¥ 


43.09 





3d ring 
at 700 



1st ring 
at 840, 
2d ring 
at 760, 
3d ring 
at 840, 
4th ring 
at 835 



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61,918 


64,240 


6i,945 



Note. — No record of tensile strength of steel ; 28 tons per square inch 
assumed. The collapsing coefficients are calculated on external diameter of 
furnace over plane part. 



STRENGTH OF BOILERS. 



21 I 





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212 



S TEA M-B OILERS. 




STRENGTH OF BOILERS. 



213 



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STEA M-BOILERS, 



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STRENGTH OF BOILERS. 



215 



Purves's Patent Furnaces. 



Official Tests made at Sir John Brown & Co. 's Works at 
Sheffield in 1889. 



^^*^^ 












































V 



Date of Test. 



5-3 



IT. flS 



Dec. 23, 1890. 



9i 
9l 
9l 



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950 
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74,834 
73.034 
73,935 

70,326 

-A -A. 
75,718 



28.8 
28.0 
27.3 
29-3 
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79,935 
72,161 
72,231 
72.. 738 
f6,i6o 

75,446 



Corrugations spaced 9" apart Not very full records kept. 

Note. — The collapsing coefficients are calculated on diameters of furnaces 
over flats. 



2l6 



STEAM-BOILERS. 



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*-. v 



STRENGTH OF BOILERS. 2\J 

Discussion of Results of Tests on Flues. — The stress 
in a thin hollow cylinder subjected to external fluid pressure 
may be calculated by an equation having the same form as 
that for a cylinder subjected to internal pressure; the equa- 
tion may be deduced by a similar method. Thus the stress 
will be 

S t' 

in which / is the pressure per square inch, r is the radius and 
/ is the thickness, both in inches. In the table we have a 
column giving the coefficient of collapse calculated by the 
expression 

PD 
T' 

in which P is the pressure, D is the diameter, and T is the 
thickness. The coefficient appears consequently to be twice the 
compressive stress in the flue at the time of collapsing. This 
coefficient is fairly regular for each style of furnace, and is 
somewhere near the tensile strength of the metal from which 
the flue is made; in some cases it is less and in some more 
than the tensile strength. Now soft steel in the form of short 
cylinders will begin to flow when the compressive stress in a 
testing-machine is about equal to the strength of pieces used 
for tensile tests. In other words, the tensile and compressive 
strengths are about equal. The furnaces tested appear, 
then, to have collapsed when the compressive stress was half 
the ultimate compressive strength of the metal. Now the 
limit of elasticity for both tension and compression, for soft 
steel, is about half the ultimate strength, so that the collapse 
occurred somewhere about the elastic limit. We should not, 
however, attribute too much importance to this considera- 
tion, but it will be better to follow ordinary practice and 
consider the equations used for calculating the safe working 



2l8 STEAM-BOILERS. 

pressure on flues to be empirical, and to depend directly on 
experiment. 

Rules for Working Pressure on Flues. — There are three 
sets of rules for working pressure on flues, which we shall 
consider; namely, those of the British Board of Trade > those 
of Lloyd 's Marine Insurance Underwriters, and those of the 
United States Inspectors of Steam-vessels. These rules are 
changed from time to time, and include certain directions to 
inspectors that need not be given here; if a boiler is built for 
inspection under these or any other rules the only safe way is 
to obtain the current edition of the rules and see that the 
boiler conforms thereto, and also that the boiler is properly 
proportioned according to the best information that can be 
obtained by the designer. 

Rules for Plain Flues. — Both Lloyd's and the United 
States Inspector^ rules use for plain flues an equation in the 
form 

89,600 X r a 
*- LD 

in which P is the working pressure in pounds per square inch* 
L is the length in feet, and T and D are the thickness and 
diameter in inches. This is Fairbairn's equation with 2 
instead of 2.19 for the exponent of T, and with a constant 



806,300 
89 , 600 = , 



so that the working pressure is made one ninth of the calci 
lated collapsing pressure by Fairbairn's rule. The use of so 
large a factor as nine shows that the rule is not considered 
adequate. Flues designed under this rule will probably be 
strong enough. 

The Board of Trade rule differs only in replacing the 



STRENGTH OF BOILERS. 



factor 89,600 by the approximate figure 99,000. The rules, 
however, require that the pressure shall not be greater than 

_ 8800 X T 
P ~ D ' 

which provides that the stress shall not exceed 4400 pounds 
per square inch. For corrugated, ribbed, or grooved furnaces 
(such as the several furnaces for which tests are given) both 
the Board of Trade and the Inspectors rules give for the 
working pressure 

1400 X T 



P = 



D 



in which P is the working pressure in pounds on the square 
inch, and Zand D are the thickness and diameter in inches. 
This rule makes the working stress 7000 pounds per square 
inch. 

Lloyd' s rule for these furnaces is given by the equation 

QT-2) 
D ' 

in which T is the thickness in sixteenths of an inch, D is the 
diameter in inches, measured over the corrugations or ribs of 
corrugated or ribbed furnaces, and over the plain part of 
Holmes' furnaces. C is an arbitrary constant having the fol- 
lowing values: 

C = 1000 for steel corrugated furnaces when the tensile 
strength of the material is under 26 tons, and corrugations are 
6 inches apart and \\ inches deep. 

C= 1259 f° r steel furnaces corrugated on Fox's or Mori- 
son's plans, tensile strength to be between 26 and 30 tons. 

C = 1 160 for ribbed furnaces with ribs 9 inches apart. 

C= 912 for spirally-corrugated furnaces. 
, C = 945 for Holmes' furnaces, when corrugations are not 
over 16 inches apart and not less than two inches high. 



220 STEAM-BOILERS. 

In this rule the use of T — 2 (in sixteenths of an inch) 
instead of T is practically an allowance for wasting of the 
plate to the extent of one eighth of an inch. The working- 
stress calculated on the assumed diameter will be found by 
multiplying by sixteen and dividing by two; in case of the 
first constant the stress is 

iooo X 16 

= 8000 

2 

pounds per square inch. 

Fire-tubes. — The thickness usually given to fire-tubes to 
insure sound welding and to provide for expanding into the 
tube-sheets is in excess of that required to prevent collapsing. 
There appears, however, to be no experiments to show the 
actual collapsing pressure for such tubes. 

The joint made by expanding the tubes into the tube- 
sheets of locomotive and cylindrical tubular boilers has been 
found both by experiment and practice to be strong enough 
to secure the tube-sheet without additional staying. It is, 
however, the custom to make part of the fire-tubes of marine 
drum-boilers thick enough to take a shallow nut outside of 
the tube-plate; without such stay-tubes there is liable to be 
leakage at the ends of the tubes. 

Girders — When a flat surface cannot conveniently be 
stayed directly, it is customary to stay the surface to girders 
properly supported at the ends or elsewhere. The crown-bars 
of the locomotive-boiler shown on Plate II, and the girders 
over the combustion-chamber of the marine boiler shown by 
Fig. 13, page 17, may be taken as examples. Again, the 
channel-irons which are riveted to the flat heads of the 
cylindrical boiler shown by Plate I act as girders. 

The load which a girder of given material can safely carry 
depends on the form and dimensions of the girder, and on the 
manner of supporting and loading the girder. Some girders, 
like those over the combustion-chamber in Fig. 13, can be 



STRENGTH OF BOILERS. 221 

calculated by the simple theory of beams; others, like crown- 
bars for locomotives and the channel-bars on Plate I, can be 
properly calculated only by the theory of continuous girders. 

A proper understanding of the theories of beams and of 
continuous girders can be obtained from standard works on 
applied mechanics. An adequate statement of even the 
theory of beams is out of place in a work on boilers; an 
incomplete statement is unadvisable, since it is liable to be 
misleading. One simple example will be worked out as an 
illustration of the use of the beam theory in boiler-design. 

As an example, we will take the girders over the combus- 
tion-chamber of the marine boiler shown by Fig. 13, page 17. 
The girders are spaced 7 inches apart, and each carries three 
stays spaced 6j inches apart. The load on each stay-bolt at 
160 pounds steam-pressure is 

7 X 6\X 160 = 7000 pounds, 

and the total load on one girder is 21,000 pounds. The sup- 
porting force at each end of the girder is 10,500 pounds. The 
span of the girder is 22^ inches, and the half-span is 11J 
inches. The bending-moment at the middle of the girder 
due to the supporting force acting upward, and to the load 
on one bolt acting downward, is 

10,500 X 1 4 — 7000 X 6J = 74,375 = M. 

Each girder is made of two plates each 5/8 of an inch thick, 
and 7 inches deep. The moment of inertia of the section of 
the girder at the middle is 

T V X 2 X i X 7 3 = /• 
The distance of the most strained fibre is 

7-^2 = 3^=^. 



222 STEAM-BOILERS. 

The working fibre-stress is consequently 

My _ 74 375 X 3^ _ „ 

/_ / - T yx2xf x 7 »- 7257 

pounds per square inch. 

Stayed Flat Plates. — The method of calculating the 
stresses in a flat plate supported at regular intervals by stays 
or stay-bolts, such as the sides of a locomotive fire-box, is 
treated in the theory of elasticity, under the heading of 
" indefinite plates which are firmly held at a system of points 
dividing them into rectangular panels. ' ' A complete solution 
of this problem is possible only when the panels are squares, 
that is, when the rows of stays are equidistant longitudinally 
and transversely. 

If the steam-pressure is represented by fi, the thickness of 
the plate by /, and the pitch of the stays by a, then the 
maximum direct stress, which is a tension at certain places 
and a compression at other, is given by the formula 

2 a* 
The maximum shearing-stress is given by the equation 

in which .E is the modulus of elasticity of the material. 

If the sheets of a locomotive fire-box, or other stayed 
pistes, have a direct tension or compression, proper allowance 
must be made for it. 

If stays or stay-bolts are in rows that are not equidistant 
each way, as for example the through-stays in the steam- 
space in Fig. 13, page 17, then the largest pitch may be used 
in the above equations. The actual stress will in such case be 
less than the calculated stress by an unknown amount. If, 



STRENGTH OF BOILERS. 223 

further, stays are arranged irregularly, the greatest distance 
in any direction may be used in the equations, but the calcu- 
lated stress may then be very different from the actual stress; 
it is, however, always the larger. 

As an example, we may calculate the stress in a side sheet 
of the locomotive fire-box shown on Plate II. Here the 
rows of rivets are four inches apart each way, the plate is 
5/16 of an inch thick, and the steam-pressure is 170 pounds. 
The maximum stress is 

The shearing-stress in this case is very much smaller. 

Now the crown-bars are bedded on and are partly sup- 
ported by the side sheets of the fire-box. The crown-sheet 
is 72 inches long and 45! inches wide, and has an area of 

72 X 45! = 328s 

square inches, and is subjected to a pressure of 

3285 X 170 = 558,450 

pounds. The distribution of this load between the side 
sheets and the sling-stays can be determined only by the cal- 
culation of the crown-bars as continuous girders, and may be 
disturbed by the expansion of the fire-box and by other 
causes. If it be assumed that the side sheets carry half the 
load on the crown-bars, then one side sheet will carry one 
fourth of 558,050, or 139,512 pounds. The side sheet is ^2 
inches long and 5/16 of an inch thick, so that the stress per 
square inch from the load on the crown-bars is 

139,512 -f 72X A = 62 °° 

pounds, — about as much as the stress calculated above. The 



224 STEAM-BOILERS. 

total compression on the side sheet is therefore about 12,400 
pounds per square inch. 

This calculation, which appears sufficiently simple, illus- 
trates the danger of making calculations by formulae without 
knowing how they are derived and how they should be 
applied. The formula for staying given above is often 
quoted without any reference to tensile or compressive stress 
on the stayed sheet, from other causes; the use of such a 
formula by one who is unfamiliar with the theory of elasticity 
may lead to serious error in design. 

Factor of Safety. — The ratio of the working pressure of 
a boiler to the pressure at which the boiler or any part of a 
boiler may be expected to fail quickly, is called the factor 
of safety for the boiler or for that part of the boiler. 

It is commonly recommended by writers that a factor of 
safety of six shall be used for boilers; probably such a factor 
would be economical for a boiler that is expected to work 
continuously for many years, as it allows a margin for deteri- 
oration. If the stresses coming on the parts of a boiler can 
be determined, a general factor of five will give sufficient 
security. If the boiler is carefully watched, a factor of four 
may be used ; many boilers are worked with this factor. The 
use of an excessively large factor of safety, for example of the 
factor nine for flues calculated by Fairbairn's equation, shows 
a lack of confidence in the method. It is proper to make 
allowance for corrosion of parts like stays: this may be done 
either by using a larger factor of safety, or by a direct allow- 
ance; thus all stays, whatever their diameters, may have an 
eighth of an inch added to the diameter to allow for corrosion. 
It is of course proper in any structure to make small but im- 
portant members, such as stays in boilers, large enough to 
place them beyond any suspicion of failure. 

Hydraulic Tests of Boilers. — It is customary to subject 
new boilers to a water-pressure considerably in excess of the 
working pressure, to discover any leaks at riveted joints, at 



STRENGTH OF BOILERS. 22$ 

the tube-sheets, or elsewhere; should there be any gross 
defect of design or workmanship it will be developed by this 
hydraulic test. Old boilers after repairs are subjected to a 
hydraulic test for the same purpose, but the pressure is not 
carried so high as for new boilers. 

The pressure applied during a hydraulic test is seldom 
more than once and a half the working pressure, and as most 
boilers have an actual factor of safet/y of not more than rive, 
and frequently of four, it is apparent that the recommenda- 
tion of some authors, that the test pressure should be twice 
the working pressure, cannot ordinarily be followed without 
danger of injuring the boiler. With a factor of safety of six 
there should be no danger of injuring the boiler by applying 
a hydraulic pressure equal to twice the working pressure. 

It should be borne in mind that some of the worst stresses 
that come on the different parts of the boilers are due to 
unequal expansion and contraction, and that such stresses are 
not set up during a hydraulic test. Finally, the fact that a 
boiler has successfully withstood a hydraulic test is not a con- 
clusive proof that it is safe; too many unfortunate explosions 
of boilers, more frequently old boilers, after a hydraulic test, 
have shown this. 

The safety of a boiler is to be insured by careful and cor- 
rect design, honest and thorough workmanship, and intelli- 
gent care in service. Forms and methods of design and 
construction that do not admit of ready calculation should be 
avoided ; in no case should the ordinary hydraulic test be 
relied upon to guarantee the strength of' parts that cannot be 
calculated with a fair degree of certainty. If such forms are 
used in any case, they ought to be tested separately to a 
pressure of two or three times the working pressure, and some 
examples of each form and size ought to be tested to destruc- 
tion. 

The boiler undergoing a hydraulic test should be carefully 
inspected, and any notable change of shape or leakage should 



226 S TEA M-B OILERS. 

be investigated to discover the cause. Frequently small leaks 
that are developed during a test are stopped at once by 
calking or otherwise, but it is preferable to mark the place 
of the leak and calk after the pressure is removed. This of 
course requires another test to find out if the calking is suc- 
cessful. 

The pressure is usually applied by filling the boiler entirely 
full of water and then pumping in enough water, by hand or 
by power, to supply the leaks and develop the pressure 
required. If the pumping is done by hand, it is desirable to 
carefully remove all air from the bo'ler to avoid the labor of 
compressing air up to the test pressure. If the pumping is 
done by power, the saving of work is of less consequence, and 
a little air remaining in the boiler will act as a cushion, and 
lessen the shocks due to the strokes cf the pump. 

New boilers are tested on the boiler-shop floor; old boilers 
are commonly tested in their settings, and in such case the 
inspection during a test is less convenient and efficient. 

It is sometimes recommended that hot water shall be used 
for testing a boiler; but there seems to be no advantage in 
so doing, as it is unequal expansion, and not merely rise of 
temperature, that sets up the unknown stresses that are so 
destructive to the boiler. Of course the use of hot water 
makes an efficient inspection during the test difficult if not 
impossible. 

When there is no other way of applying the hydraulic test 
to a boiler in its setting, the boiler may be quite filled with 
water, and then a light fire may be started in the furnace. 
The expansion of the water will develop the required pressure 
at a much less temperature than that of steam at the same 
pressure, and with less danger should the boiler fail. This 
method cannot be recommended for general use; and in case 
it is followed care must be taken not to exceed the desired 
pressure. 



STRENGTH OF BOILERS. J2/ 

Hydraulic Test to Destruction. — In 1S88 a boiler-shell, 
made to represent a part of the shell ot a gunboat boiler, was 
tested by hydraulic pressure at the Greenock Foundry,* with 
the intention of bursting it. The shell was 1 1 i'eet long and 
7 feet 8 T 3 <- inches mean diameter. It was made of three sec- 
tions of 19/32 plate, triple-riveted, with butt-joints and double 
cover-plates at the longitudinal joints, and lapped and double 
riveted at the ring seams. The rivets were staggered for both 
longitudinal and ring seams. The end-plates were 20/32 
thick, and stayed with through-stays and washers, spaced 14 
inches on centres. The stays were ij inches in diameter; 
the screws at the ends of the stays were 2] inches in diameter. 
Finally, it may be said that the shell was designed to fulfil 
the Admiralty specifications for a working pressure of 145 
pounds per square inch. The workmanship was of the same 
degree of excellence usual for boiler-work at that establish- 
ment. 

First Test. — The shell was first subjected to the working 
pressure of 145 pounds, and showed a slight alteration of form 
due to the tendency of internal pressure to give it a true cylin- 
drical form. The pressure was then raised to the Admiralty 
test pressure of 235 pounds, and then to 300 pounds without 
developing leaks. There were some minor changes of form 
due to the increase of pressure. The pressure was then 
removed and the shell returned to its original dimensions. 

Pressure was then raised to 330 pounds, when there was a 
slight leak at the manhole door. At 450 pounds pressure 
the leak at the manhole door exceeded the capacity oi the 
pumps. There was also a slight leak at the corners ot two 
butts. The manhole was then strengthened — no other repairs 
were made. 

Second Test. — Pressure was raised to 350 pounds and 
developed a small leak at the manhole. There were slight 

* Trans. Inst. Naval Arch., vol. xxx. p. 285. 



228 S TEA M- BOILERS. 

leaks at the butt-straps, which were calked at the end of the 
test. The manhole, however, leaked so that the test was 
stopped. 

Third Test. — After additional bolts were put into the 
manhole cover the pressure was raised to 350 pounds with- 
out leakage. At 360 pounds the manhole began to leak, and 
at 580 pounds the test was stopped on that account. The 
butt-straps opened visibly at the calking and leaked more 
than before. 

Fourth Test. — The butt-joints were again calked and 
additional pumps were employed. The shell was again tight 
at 350 pounds and the pressure was carried to 620 pounds, at 
which there was a good deal of leakage at the butt-straps. 
Only one or two rivets showed signs of leakage; there 
appeared to be no difference between the hand and machine 
riveting in this respect. At the pressure of 620 pounds the 
entire capacity of the pumps was required to supply the 
leakage. 

. The distortion of the shell was very marked at the higher 
pressures, and increased with the pressure; thus the ends- 
bulged an inch at 520 pounds, about \\ inches at 580 pounds, 
and nearly two inches at 620 pounds. The sides bulged more 
irregularly, but to the extent of nearly an inch at 620 pounds. 
The stays drew down uniformly 1/64 of an inch at 520 
pounds, 2/64 at 580 pounds, and 4/64 at 620 pounds. They 
increased in length 2^ inches at 520 pounds, 3J inches at 
580 pounds, and 3f inches at 620 pounds; this accounts for 
the bulging of the end-plates. 

The mean tensional strength of the plates from which the 
shell and butt-straps were made may be taken at 61,500 
pounds. At 620 pounds the tension on the plates between 
the rivet-holes was ^7,504 pounds, or 93 \ per cent of the 
strength oi the ^olid plate, and there was no serious disturb- 
ance of the structure. The ring seams increased in diameter 
about f of an inch, and the shell bulged out between them. 



STRENGTH OF BOILERS. 220, 

The various portions of the boiler acted in harmony and 
showed no special weakness at any point. The butt-joints 
had the rivets spaced 5 j- inches on centres to give a percen- 
tage of 83.7 per cent of the plate, and this may have caused 
the leakage found there. The riveting appeared to be 
reliable at the extreme pressure reached. This test seems to 
show that a boiler will give signs of weakness long before it 
will fail. Such signs of weakness should be carefully investi- 
gated : if there is any local weakness or deterioration, repairs 
or alterations may be made; if there are evidences of general 
deterioration, the working pressure must be reduced, or 
better, the boiler may be replaced by a new one. 

Boiler-explosions. — The great destruction of life and 
property that is liable to be caused by a violent boiler-explo- 
sion makes it imperative that the causes should be carefully 
investigated, to the end that explosions may be prevented. 

With this in view the boiler and its parts, and any wreck 
or evidence of destruction caused by the explosion should be 
left undisturbed until the scene of the explosion can be 
examined by a competent engineer. Of course if any persons 
are injured by the explosion they must be rescued and cared 
for immediately, and also any building or structure that is so 
injured as to threaten life or safety must be attended to at 
once; but it should be borne in mind that the examination by 
the engineer for the purpose of determining the cause of the 
explosion is also in the interest of humanity, since its aim is 
to avoid future explosions. All idle or simply curious per- 
sons should be excluded from the scene of the explosion, more 
especially as such persons are apt to disturb or even carry 
away things that may be of importance ?.n the study o> the 
cause and history of the explosion. If the explosion is 
accompanied by loss of life or injury to person or property, 
it will be followed by a le^al investigation in which the testi- 
mony of the engineer or engineers who have examined the 
scene of the explosion will be of prime importance, as it will 



23O STEAM-BOILERS. 

have a large influence in locating responsibility for the 
disaster. 

While various causes may lead to boiler-explosion, it is 
unfortunately true that by far the greater part of violent 
explosions are due to the fact that the boiler is too weak to 
endure service at the regular working pressure. A new boiler 
may be weak through defective design or workmanship; 
there can be no excuse for the explosion of a new boiler from 
weakness, and such explosions in good practice are rare. An 
old boiler is liable to become weak through local or general 
corrosion or other deterioration; this amounts to saying that 
a bciler will eventually wear out. 

The length of time that a boiler will endure service 
depends (i) on the design, (2) on the thickness of plates and 
the quality of the metal, (3) on the workmanship, (4) on the 
care given it, and (5) on the quality of the feed-water. 
Definite figures cannot be given for the life of a boiler, since 
it depends on so many things. The following table gives the 
number of years several kinds of boilers can endure regular 
service if they are properly built and cared for: 

Lancashire, low-pressure 1 5 to 20 years. 

Locomotive type, stationary 12 to 1 5 

Locomotive-boilers , 8 to 12 

Vertical boilers 10 to 1 5 

Vertical boiler with submerged tubes... . 14 to 18 

Horizontal cylindrical tubular 15 to 20 

Scotch marine boiler 12 to 1 5 

Water-tube boiler 12 to 16 

Pipe or coil boiler 5 to 8 

By water-tube boiler is here meant a boiler with a shell 
or drum containing a considerable body of water. By pipe 
or coil boiler is meant a boiler made up of pipe and pipe- 
fittings, with a separator. 



STRENGTH OF BOILERS. 23 j. 

Horizontal boilers will require one, and vertical boilers two 
extra sets of tubes, before the shell is condemned. A loco- 
motive-boiler will require two extra sets of tubes, and the 
entire fire-box will be renewed once in the life of the boiler. 

If boilers are subjected to careless or ignorant abuse, they 
may be used up in a fraction of their proper time of service, 
especially if cheaply built. This will account for the numer- 
ous explosions of sawmill boilers and agricultural boilers. 

It has been pointed out that leakage is frequently a sign 
of weakness; a perversion of this idea leads to the assumption 
that a boiler is safe as long as it can be kept from leaking. 
Too many boiler-explosions have this history: The boiler, 
after long and satisfactory service, began to leak; a cheap 
man was employed to repair the boiler, the repairs consisting 
mainly of excessive calking to stop the leaks; soon after the 
repairs, perhaps the first time the boiler was fired up, it 
exploded violently. A fit conclusion of the history is to 
ascribe the explosion to some obscure cause or to carelessness 
of the attendant, if he was killed by the explosion. 

Serious injury may be caused by overheating any part of 
the heating-surface, due to low water, to defective circulation, 
or to deposits of non-conducting substance on the plates or 
tubes. The overheated member, or plates, of the boiler may 
burst or collapse, and such failure may lead to an explosion 
of the boiler, but frequently the escape of steam and water 
will check the fire and relieve the pressure on the boiler. 
Local failures are dangerous to the boiler attendants, especially 
in a confined fire-room, as on shipboard. Unless there is 
direct evidence of overheating, either from known circum- 
stances before the explosion or from signs on the boiler after 
explosion, the cause of the failure should be sought elsewhere. 

If a boiler shows siems of low water or of overheating the 
fire should be checked by any effectual means. The most 
ready way of checking the fire is to close the ash-pit doors and 
throw ashes onto the fire. If there are no ashes at hand, then 



232 STEAM-BOILERS. 

fresh fuel may be used instead, since its first effect is to deaden 
the fire. There will be time for caring for, or drawing the fire 
before the fresh fuel is fairly in combustion. An attempt to 
draw the fire without first deadening it is liable to give a fierce 
combustion for a short time; moreover, more time is required 
to draw the fire. If the furnace has a dumping-grate, the fire 
may be immediately thrown into the ash-pit without waiting 
to deaden it. The damper should be left open so that if a 
rupture occurs the steam may escape up the chimney. Mean- 
while the steam made by the boiler should be disposed of by 
allowing the engine to run or by any other means, for exam- 
ple by opening the safety-valve, provided that it is merely a 
case of overheating, not accompanied by excessive pressure. 
It will probably be well to start the feed-pumps or to increase 
the supply of feed-water. Should the introduction of feed- 
water be badly arranged so that a large volume of cold water 
will be thrown onto a heated plate, it is possible that starting 
the feed-pump may cause a contraction which will start a 
rupture. 

It has been found by experiment that boiler-flues that 
have been purposely allowed to become bare and overheated 
have been saved by suddenly directing a stream of cold feed- 
water upon them, though such treatment may make them 
leak at the joints. The heat stored in such hot plates is 
insignificant as compared with the heat in the water and steam 
in the boiler. 

Excessive pressure, especially if it is enough to give good 
reason to fear an explosion, is more difficult to deal with; the 
chances of success are less and the risks are greater than when 
the water is low, but the pressure is not excessive. If possi- 
ble the fire should be checked and the pressure relieved. The 
first may be done by throwing on ashes or cold fuel, and the 
second by running the engine at full load. It is at least 
doubtful whether starting the feed-pump will reduce the 
pressure fast enough to do much good, and on the other hand 



STRENGTH OF BOILERS. 233 

there may be cases where such action would start an explo- 
sion. It is not best to open the safety-valve, since the sudden 
opening of a large safety-valve gives a shock which may 
determine the explosion. Some explosions have been re- 
ported that occurred immediately after the safety-valve 
opened. 

A large amount of energy is stored in the steam and water 
in a boiler in the form of heat. An idea of the amount of 
energy in any given case may be obtained by a simple calcu- 
lation. Thus the cylindrical boiler shown on Plate I, at 150 
pounds pressure by the gauge, will contain 6600 pounds of 
water and 22 pounds of steam. Taking 165 pounds absolute 
to correspond to 150 pounds by the gauge, we find from a 
table of the properties of steam that 338 thermal units are 
required to raise one pound of water from freezing-point to 
366 F., corresponding to 165 pounds absolute. Now one 
thermal unit is equivalent to 778 foot-pounds of work. Con- 
sequently the energy stored in the hot water in the boiler, 
calculated from freezing-point, is 

6600 X 778 X 338 = 1,736,000,000 foot-pounds. 

After the water is heated to 366 F. there will be required 
855.6 thermal units to vaporize one pound into steam at 165 
pounds absolute. But 83.6 thermal units will be expended 
in changing the volume of the fluid when it passes from water 
into steam, leaving 772 thermal units for the internal heat of 
the steam. Consequently the heat stored in a pound of 
steam is 772 -\- 338 thermal units. The equivalent energy 
stored in 22 pounds of steam is 

22 X 778 X (772 + 338) = 19,000,000 foot-pounds. 

The first point to be noticed is, that there is many times 
as much energy in the water as in the steam; and the second 
is, that even a small fraction of the stored energy is suffi- 



234 STEAM-BOILERS. 

cient to account for all the destruction caused by a boiler- 
explosion. 

The circumstances of the boiler-explosion will determine 
how much of the energy stored in the steam and hot water 
will be developed and how it will be applied. Even in a par- 
ticular case it is seldom possible to make proper estimates, 
nor does there appear to be any advantage from doing so. 
It is, however, curious to know that if the steam and water 
in the boiler under discussion were placed in a large cylinder 
with non-conducting walls and allowed to expand behind a 
piston, down to the pressure of the atmosphere there would 
be developed 138,000,000 foot-pounds. And further, if this 
work were expended in raising the boiler and its contents 
against the attraction of gravity, it could lift them a mile 
high. 



CHAPTER VIII. 
BOILER ACCESSORIES. 

In this chapter will be described various fittings, attach- 
ments, and accessories for steam-boilers. 

Valves are used to control and regulate the flow of fluids 
in pipes. They are variously named after their forms or uses, 
such as globe valves, angle-valves, straightway valves, and 
check-valves. 



C 




Fig. 83. 

Globe Valves are named from the globular form of their 

cases. The case is separated into two parts by a diaphragm 

with a passage through its horizontal part, as shown in Fig. 

83. The fluid enters at the right, passes under the valve, and 

235 



236 



STEAM-BOILERS. 



out at the left. The valve is shut by screwing down the 
handle on the valve-spindle. A stuffing-box around the 
valve-spindle prevents leakage of fluid. In this valve the seat 



^^ 



S. 




5 PIPE TAP 



Fig. 84. 



is rounded, and the valve face is a ring of a peculiar composi- 
tion, let into the valve at R. When the valve is shut, this 
composition is squeezed down onto the seat and makes a 
tight joint. 

If the fluid enters the valve from the right-hand side, the 



BOILER ACCESSORIES. 



2tf 



valve-spindle may readily be packed to prevent leakage while 
the valve is closed. If the fluid entered the valve at the 
other end, it would be necessary to shut off the fluid from 
the entire pipe in order to pack the valve. 

Angle-valves. — This form of valve, shown by Fig. 84, 
has an inlet at the bottom and an outlet at one side, it may 
take the place of an elbow at a bend in piping. The valve 
is made in two parts. The upper part carries a ring of sore 
metal which forms the bearing-surface. The lower part has 
ribs or wings which enter the opening through the valve-seat 
and guide the valve to its seat. The valve-spindle has a 




Fig. 85. 



screw at the upper end which passes through a yoke entirely 
outside of the body of the valve. 

The body of the valve is made of cast iron. The valve, 



2 3 8 



S TEA M-B OILERS. 



valve-seat, valve- spindle, and stuffing-box follower are made 
of brass or composition. 

This form of valve is frequently used for the stop-valve 
between the boiler and the main steam-pipe. 

Straightway or Gate Valve. — This form of valve gives 
a straight passage through the valve, and offers very little 
resistance to the flow of fluids when it is open. Fig. 85 
represents a Chapman valve, in which the valve is wedge- 



-c 



ff^ 





Fig. 86. 



shaped and is forced against a wedge-shaped seat. The valve- 
spindle is held at a fixed height by a collar, and draws up or 
forces down the valve to open or close it. The body of the 
valve is of cast iron; the valve, valve-spindle, and stuffing-box 
are ot brass; the valve-seat is a soft composition. 

Fig. 86 represents a Peet valve, which has the faces of the 
valve-seats parallel. The valve itself is made in two pieces, 



BOILER A CCESSORIES. 



239 



between which is a peculiar casting, U shaped at the bottom 
and with wedge-shaped lips at the top. When the valve is 
shut this casting rests on the bottom of the valve body, and 
the two halves of the valve are thrown against the parallel 
valve-seats by the wedge-shaped lips of the casting. When 
the valve is opened this casting hangs between the two halves 
of the valve by the under side of the wedge-shaped lips. 

Check-valves allow fluids to pass in one direction, but 
not in the other. Fig. 87 represents a lift check- valve; it 





Fig. 87. 



Fig. 88. 



resembles a globe valve without a valve-spindle. Fluid 
entering at the left will lift the valve and pass out at the 
right. Should the current be reversed the valve will be 
promptly closed. 

Fig. 88 represents a swing check-valve. It offers less 
resistance to the flow of fluid than the valve shown above, 
and there is less chance that foreign matter will lodge on the 
valve-seat. The valve has some looseness where it is fastened 
to the swinging arm, so that it may properly seat itself. 

A feed-pipe must always have a check-valve to keep the 
boiler-pressure from acting on the pump, or injector, when it 
is not at work. It automatically opens to allow water to pass 
into the boiler. There should also be a stop-valve (a globe or 
gate valve) near the boiler which can be shut at will; thus 
when the check-valve shows signs of leaking the stop-valve 



240 STEAM-BOILERS. 

may be shut, and then the check-valve may be opened and 
examined. 

Safety-valves are intended to prevent the pressure oi 
steam from rising to a dangerous point. In order to accom- 
plish this, the effective opening of the valve should be suffi- 
cient to discharge all the steam that the boiler can make 
when urged to its full capacity. The effective opening is 
equal to the circumference of the valve-seat multiplied by the 
lift of the valve, if the valve-seat is flat; if the valve-seat is 
conical, the lift should be measured at right angles to the 
seat. Then if / is the vertical lift and if a is the angle which 
the seat makes with the vertical, the effective lift is 

/ sin a, 

The lift of a safety-valve rarely exceeds i/io of an inch. 
A two-inch pop safety-valve, made by the Crosby Gauge and 
Valve Co., and tested at the laboratory of the Massachusetts 
Institute of Technology, was found to lift from 0.07 to 0.08 
of an inch. The valve had a conical seat with an angle of 
45 . The actual flow was about 95 per cent of the calculated 
flow for this valve. 

The amount of steam that a boiler can make may be 
estimated from the grate-area, the rate of combustion, and the 
evaporation per pound ot coal. The first item is fixed, and 
the other two, though somewhat indefinite, may be estimated 
from the type of boiler and the conditions under which it 
works. 

For example, a factory boiler having a grate 5 feet by 6 
feet may be assumed to burn 18 pounds of coal per square 
foot of grate-surface per hour, and to evaporate 8 pounds of 
water per pound of coal. It will therefore generate 

5X0X18X8 

< : -; = 1.2 pounds of steam per second. 

60 X 60 v l 

The amount of steam which will be delivered by a safety- 



BOILER ACCESSORIES. 24 I 

valve may be calculated by an empirical equation proposed 
by Rankine; it may be written 

W=A— t 
70' 

in which W is the weight of steam in pounds delivered per 
second, A is the effective area of discharge in square inches, 
and / is the absolute pressure of the steam in pounds per 
square inch. 

If the weight of steam to be discharged per second is 
known, then this equation may be used to calculate the 
effective area; and will then read 

A - 70W 

In the example given above the weight of steam per second 
is 1.2 pounds. If the steam-pressure is 100 pounds absolute 
(85.3 by the gauge), then the effective area must be 

70 X 1.2 

A = =0.84 

100 

of a square inch. If the effective lift be assumed to be 0.075 
of an inch, the circumference of the valve-seat should be 

0.84 -f- 0.075 = JI - 2 inches, 
and the diameter should be 3.5 inches. 

A common rule requires that there shall be an area of 1/3 
of a square inch through the valve-seat for each square foot 
of grate-surface. It so happens that this rule gives almost 
identically the same result as that just calculated for the above 
example; thus: 

5 X 6 



10 square inches, 



v/ 



— = 3.5 -f- inches, diameter. 



242 



STEAM-BOILERS. 



Should the size of the valve determined by the two 
methods be different, the larger one must be taken ; for the 
engineer will desire to fulfil the requirements of the first 
method for the sake of safety, and the requirements of the 
second method must be fulfilled if the boiler is to pass inspec- 
tion. 

Lever Safety-valve. — The general arrangement and some 
of the details of a well-made safety-valve are shown by Fig. 

8 9 . 



I 



WEIGHT 
116 LBS. 



CENTER OF GRAVITY 
OF LEVER 

WEIGHT OF LEVER 42 LBS. 

WEIGHT OF VALVE AND 

SPINDLE 15 LBS. 




Fig. 89. 



The body of the valve is of cast iron, and has an opening 
at one side from which the escaping steam is led out of 
the boiler-room through an escape-pipe. The valve and 
valve-seat are of brass or composition; the bearing-surface is 
at an angle of 45 with the vertical. The load is applied by 
a steel spindle, to a point beneath the bearing-surface so that 
the valve is drawn down to its seat. The spindle passes 
through a brass ring in the cover to the valve-casing. The 
load is applied by a lever with a fulcrum at A and a weight 
at D. It is steadied by guides cast on the cover of the 
casing; in the figure the valve and body are shov/n in section 
but the spindle, lever, guides and weight are shown in eleva- 
tion. 

It is important that the pins ai: A and B shall be loose in 
their bearings, and that the spindle shall be free where it 



BOILER ACCESSORIES. 243 

passes through the top of the valve-case, so that the valve may 
not fail to rise even if the working parts are rusted a little. 

After a safety-valve has blown off it is liable to leak a 
little, and such leakage is likely to injure the bearing-surface. 
In this way safety-valves sometimes get leaky and trouble- 
some. The proper wa)' is to regrind the valve and make it 
tight, but if the boiler attendant is careless he may try to 
stop the leak by jamming the valve on its seat. This may 
be done by hanging on extra weight, or wedging a piece of 
wood or metal against the lever. To remove temptation, it 
is well to have the guides for the lever open at the top, and 
also to cut off the lever to just the proper length so that the 
weight cannot be slid farther out. A short lever and a heavy 
weight are better, for this reason, than a lighter weight and a 
longer lever. 

In order to make a calculation of the pressure at which a 
safety-valve will blow off, we must know the diameter of the 
valve, the weight of the valve and valve-spindle, the length 
of the lever and the weight hung at its end, and the weight 
and centre of gravity of the lever. This last may be found 
by calculation, or more simply by balancing the lever on a 
knife-edge. 

In the example shown by Fig. 89 the valve has a diameter 
of 5 inches and an area of 

^ 6 ^= 19.635 

square inches, on which the steam presses. 

The valve and spindle weigh 15 pounds; this is applied 
directly at the valve. The weight of 115 pounds at the end 
of the lever, is 56 inches from the fulcrum at A. It is equiva- 
lent to a weight of 

ili*-?^ = l6l0 



244 STEAM-BOILERS. 

pounds at the valve. The weight of the lever is 42 pounds* 
applied at the centre of gravity C, 20 inches from the fulcrum.. 
It is equivalent to a weight at the valve of 

42 X 20 

= 210 

4 

pounds. The total equivalent weight, or the load on the 
valve, is 

15 -\- 1 6 10 + 2I ° = 1835 pounds. 

Since the area of the valve is 19.635 square inches, the 
steam-pressure per square inch required to lift the valve will 
be 

1835 -T- 19-635 = 93-46 pounds. 

Problems concerning the loading of a safety-valve may be 
conveniently stated and solved by taking moments about the 
fulcrum ; that is, by multiplying each weight or force by its 
distance from the fulcrum. 

Let the weights of the valve, spindle, lever, and weight 
be represented by V, S, L, and W. Let a be the distance of 
the weight from the fulcrum and b be the distance from the 
fulcrum to the valve, while c is the distance of the centre of 
gravity of the lever from the fulcrum. 

The moment of the weight is Wa t and the moment of the 
lever is Lc. The moment of the valve and spindle is (V -\-S)b. 
All three moments act downward, and their total effect is equaL 
to their sum, 

Wa + Lc + (V+S)&. 

If the diameter of the valve is d y then the area is %nd*. 
Representing the steam-pressure above the atmosphere by/* 
the force acting on the valve is 

nd* 



BOILER ACCESSORIES. 245 

and the moment of that force is 

TTd* , 

This moment acts upward and, when the valve lifts, will 
be equal to the total downward moment. So that the equa- 
tion for calculating the load on a lever safety-valve is 

pb— = Wa + Lc + (V+ S)&. 

This equation gives for the steam-pressure at which the 
valve shown by Fig. 89 will lift 

[Wa + Lc+ (V+ S)5] 
p ~ " nd'b 

_ 4(1 1 5 X 56 + 42 X 20 + 1 5 X 4) 
•'• p ~ 3.H16X 5 2 X 4 

.-. p = 93.46 pounds, 

as found by the previous calculation. 

For a second example let us find the distance at which 
the weight of the valve shown by Fig. 89 must be placed 
from the fulcrum in order that the valve will blow off at 50 
pounds above the atmosphere. 

Solving the general equation for a, we have 

nd* 

pb—- Lc- (V+S)& 



a = 



W 



50 X 4 X 3 '\ 41 X 5 2 - 42 X 20 - 1 5 X 4 

. . * = A - 

115 

,\ a r= 26.32 inches. 



246 S TEA M-F OILERS. 

For a third example find the weight which should be hung- 
at the end of the lever if the valve is to blow off at 30 pounds 
above the atmosphere. 

Here we have 

nd 2 

pb Lc-(V-\-S)b 

W= * u 



30 X 4 X iL - — X5 -42X20-15x4 



.*. W 



56 
.•. W = 26 pounds. 

These last two problems can of course be stated and 
solved much after the first manner applied to the first problem, 
but the work, which will amount in the end to the same' 
thing, cannot be so well arranged nor so easily done. 

Pop Safety-valve. — A defect of the common lever 
safety-valve is that it does not close promptly when the 
steam-pressure is reduced, and it is apt to leak after it has. 
returned to its seat. 

The valve shown by Fig. 90 has a groove turned in the 
flange which projects beyond the bearing-surface, and there is 
another groove between the outer edge of the valve-seat and a 
ring which is screwed onto the valve-seat. When the valve 
lifts the escaping steam is twice deflected, once by the groove 
in the valve and again by the groove at the valve-seat. The 
reaction of the steam assists the pressure of the steam on the 
under surface of the valve, and suddenly opens the valve to 
its full extent. The valve stays wide open till the steam- 
pressure in the boiler has fallen a few pounds below the blow- 
ing-off pressure, and then the valve shuts as suddenly as it 
opens. 

The ring which is screwed onto the valve-seat has a number 



BOILER ACCESSORIES. 



247 



of holes drilled through it to allow steam to escape from the 
groove at its upper surface. It may also be screwed up or 




Fig. go. 

down to adjust its position; a screw at the side of the case 
clamps it when adjusted. The action of the valve is regulated 



248 STEAM-BOILERS. 

by the number of holes in the ring and by its vertical posi- 
tion. 

This valve is loaded by a helical spring. The tension of 
the spring and the load on the valve is regulated by a sleeve 
which is screwed down through the top of the valve-case. It 
is of course possible to load a plain safety-valve in a similar 
way, or to load a pop-valve with a lever and weight. The 
valve is extended up in the form of a thin shell to guard the 
spring from the escaping steam. The valve-spindle is ex- 
tended through the top of the case, and may be pulled up 
by a lever when it is desired to ease the valve off from its 
seat. A drip at the lower right-hand side of the case draws 
off water which may collect in the case. 

The valve and its seat, the adjusting-ring on the seat, the 
valve-spindie, and the bearing-pieces on the spring are all 
brass. There is also a brass ring inside the shell that extends 
down from trie co^er and incloses the spring. There should 
be a little clearance between this brass ring and the shell on 
the valve so that the valve shall not be cramped. The entire 
valve-casing, which is made in four parts, is of cast iron. 

The closeness of regulation by a safety-valve depends 
mainly on the width of the bearing-surface. Thus a valve 
with a narrow bearing-surface will close after the pressure in 
the boiler is reduced a few pounds ; a valve with a wide bear- 
ing-surface will stay open till the pressure has suffered a 
serious reduction. By making the bearing-surface very narrow 
the reduction of pressure maybe made as small as two pounds. 
For example : a certain valve was made to open at 100 pounds 
and to close at 98 pounds. When the bearing-surface is 
narrow it must be made of hard, dense metal to endure the 
pressure concentrated on it. Hard bronzes, compositions 
and nickel alloys are used for this purpose. 

A safety-valve should be set by trial, to blow off at the 
required pressure as shown by a correct steam-gauge. A 
safety-valve should occasionally be lifted from its seat to 



BOILER ACCESSORIES. 249 

insure that it is in proper condition. An unexpected opening 
of a safety-valve or continued leakage shows lack of attention 
to duty on the part of boiler attendants. While the safety- 
valve for a boiler should be able to deliver all the steam it can 
make, it may be considered that the proper function of a 
safety-valve is to give warning of excessive pressure. The 
safety of the boiler must always depend on the faithfulness 
and intelligence of the boiler attendants. 

Inspection laws commonly require that every boiler shall 
have two safety-valves, and that one of them shall be locked 
up in such a manner that it cannot be overloaded by accident 
or design. 

Water-column. — The position of the water-level in a 
boiler is indicated either by a water-glass or by gauge-cocks or 
by both. These may be connected directly to the front end 
of the boiler, or they- may be placed on a fitting known as a 
water-column or combination. Fig. 91 shows a good form of 
water-column. It is a cast-iron cylinder connected to the 
steam-space at the top and to the water-space near the 
bottom. The normal position of the water-level is near the 
middle. There is at the bottom a globular receiver into 
which deposits from the water may settle and be blown out 
at will. 

In one side of the water-column are brass fittings for the 
water-glass, which is a strong tube of special make. The 
glass tube passes through a species of stuffing-box in the brass 
fitting. The joint is made tight by a rubber ring which fits 
on the tube and is compressed by a follower screwed onto it. 
Each fitting has a valve by which steam may be shut off when 
the tube is cleaned or replaced. A cock at the bottom drains 
water from the tube; for this purpose the lower valve is 
closed and the cock is opened. Stout wires at the side of the 
glass tube guard it from injury. 

If either valve leading to the water-glass is closed, the 
level of the water will rise in the tube. If the upper valve is 



250 



S TEA M-B OILERS. 



closed, the steam in the upper part of the tube is gradually 
condensed by radiation, and is replaced by water entering 
from below. If the lower valve is closed, the condensation 
of steam from radiation will accumulate and gradually fill the 
tube. 

Gauge-glasses are very brittle and, though carefully 
annealed, are under considerable stress from unequal cooling. 




WATER 
CONNECTION 



Fig. 91. 

Before a tube is put in it may be cleaned by pouring acid 
through it, or by drawing a bit of waste through on a string. 
A wire should never be forced through a glass tube, for the 
slightest scratch may start a break which will end in reducing 
the tube to small pieces. When a tube is in place it may be 
cleaned by closing the lower valve and opening the drainage- 
cock and allowing steam to blow through. 

When a boiler is left banked overnight the water-glass 



BOILER ACCESSORIES. 251 

should be shut off, since a breakage may result in drawing the 
water in the boiler down to the level of the lower end of the 
tube. 

In addition to the water-glass, which shows at all times the 
level of the water, the water-column carries three gauge- 
cocks. One is set at the desired water-level, one a little 
above and one a little below. Steam from the steam-space, 
through the upper gauge-cock, becomes superheated as it 
blows into the atmosphere and looks blue. The lower cock 
discharges hot water from the water-space, which flashes into 
steam as it escapes, but it has a white color, which is very 
distinct from that of the jet from the steam-space. A good 
fireman occasionally tests the position of the water-level by 
using the gauges to be sure that the indication by the water- 
glass is not erroneous. Engineers on locomotives, and boiler 
attendants where very high-pressure steam is used, often 
prefer to depend entirely on the gauge-cocks, and dispense 
with the water-glass, which may be annoying or dangerous 
when it breaks. 

The water-column shown by Fig. 91 has an alarm-whistle, 
which shows above the main casting, at the right. It is con- 
trolled by two floats inside the cylinder; one float at the top 
opens the valve leading to the whistle when the water-level 
is too high, the other near the bottom blows the whistle when 
the water-level is too low. 

If the fire is stirred up under a boiler which has had the 
fire banked, the water-level rises in the water-glass; the 
reason being that the circulation is from the front of the boiler 
to the rear, and that this circulation is maintained by a differ- 
ence of level between the front and rear ends. On the con- 
trary, the water-level falls when a boiler which has been 
steaming freely is checked. 

Steam-gauges.— The pressure of the steam in a boiler is 
shown by a spring-gauge which has the external appearance 
shown by Fig. 92. The essential part is a flattened brass 



252 STEAM-BOILERS. 

tube bent into the arc of a circle as shown by Fig. 93. The 
section of the tube may be an oval, or it may have two longi- 
tudinal corrugations as shown by Fig. 94. 




Fig. 92. 

Pressure inside of such a tube makes it bulge and tends 
to straighten it. One end is fixed and is in communication 




Fig. 93. Fig. 94 

with the space where the pressure is to be measured. The 
other end is closed and is free to move. It is connected by 
a link to a lever which bears a circular rack in gear with a 



BOILER ACCESSORIES. 253 

pinion. The motion of the free end of the tube is multiplied 
and is shown by the motion of a needle on the pinion. The 
scale on the dial is marked by trial to agree with the indica- 
tions of a mercury column or of a standard gauge. A hair- 
spring on the pinion (not shown in Fig. 93) takes up the back- 
lash of the multiplying-gear. 

The long, flexible spring-tube is liable to vibrate to an 
undue extent when the gauge is exposed to the jarring of a 
locomotive. To avoid this difficulty, two short stiffer tubes 
have their ends connected to a more effective multiplying 
device, shown by Fig. 95. The greater number of joints in 
this device makes it less sensitive than the other form. 




Fig. 95- 

Since the spring-tube changes its shape if the temperature 
changes, hot steam should not be allowed to enter it. An 
inverted siphon or U tube filled with water is, therefore, 
interposed between the gauge and the steam from the boiler. 

Safety-plugs, or Fusible Plugs, as shown by Fig. 96, are 
made of brass and provided with a core of fusible metal. If 
the plate into which they are screwed is in danger of over- 
heating, the fusible metal will melt and run out, and steam 
and water will blow into the furnace. If the fire is not put 



254 STEAM-BOILERS. 

out, it will at least be checked and the attention of the fire- 
man will be attracted. 

The melting-point of fusible metals is not always certain, 
and the plugs not infrequently blow out when there is no ap- 
parent cause. On the other hand, they sometimes fail to act 
when the plate is overheated. If the plug is covered with 
incrustation, the fusible metal may run out without giving 
warning. 

The following are some of the places where a fusible plug 
is used: 

In the back head of a cylindrical tubu- 
lar boiler, about three inches above the 
top row of tubes. 

In the crown-sheet of a locomotive 
fire-box. 

In the lower tube-sheet of a vertical 
boiler; or sometimes in one of the. tubes a 
Fig. 96. little above that tube-sheet. 

In the lower side of the upper drum of a water-tube 
boiler. 

The fusible composition has a conical form so that it can- 
not be blown out by the pressure of the steam. 

Foster Reducing-valve. — When steam is desired at a 
less pressure than that of the boiler, it is passed through a 
reducing-valve like that shown by Fig. 97. The valve H is 
held open by the spring aty, acting through the toggle-levers 
a, until the steam-pressure in the exit-pipe B, pressing 
on the diaphragm D, is able to overcome the spring and 
close the valve. The pressure at which this may occur is 
determined by the tension of the spring, which may be 
regulated by the screw at K. It is expected that the 
valve will be drawn up so as to admit just the proper 
amount of steam to the exit-pipe B to maintain the de- 
sired pressure in it. Valves for this purpose are liable to 
work intermittently, i.e. they close till the pressure falls 




BOILER ACCESSORIES. 



255 



below the proper point, then they open and raise the steam- 
pressure above that point. The valve is a species of throt- 
tling-valve, and therefore cannot be expected to remain tight. 
If the machinery supplied by the reducing-valve is liable to 




^^j 



Fig. 97. 
be injurea by excessive pressure, there must be a stop-valve 
beyond the reducing-valve. The stop-valve must be closed 
when no steam is drawn, and must be used to regulate the 
supply of steam until the amount drawn exceeds the leakage 
of the reducing-valve. 

The Damper-regulator shown by Fig. 98 places the 
damper in the flue leading to the chimney under the control 
of the steam-pressure, so that if the pressure of the steam 
falls, the damper is opened wider to quicken the fire. The 
pressure of the steam in the boiler is communicated through 
the pipe a to the lower surface of a diaphragm, and lifts the 
loaded lever b y which stands half-way between the stops at 
the middle of its length when the steam-pressure is at 
the proper point. Should the steam-pressure rise above the 



256 



S TEA M-B OILERS. 



proper point it raises the lever and opens a small piston-valve 
at c, and water from a hydrant flows into d and presses on a 
piston which lifts the weights at e and so shuts the damper. 




Fig. 98. 
The weighted head e of the piston is connected by a chain to 
the lever/, and closes the valve c as it rises, and so shuts off 
the water from the hydrant. 

A regulator of the same form attached to a throttle- 
valve acts as a reducing-valve, and regulates the pres- 
sure below the valve with a variation of less than one 



BOIL ER A CCESSORIES. 



257 



pound. Fig. 99 shows the steam-valve used when the 
Locke regulator acts as a reducing-valve. The valve is 
a double valve which is nearly balanced, but with a slight 
tendency to rise under steam-pressure, as the lower valve 
is the larger. The cylindrical part of the valve is cut 
into V notches, so that the supply of 
steam is regulated to a nicety when the 
valve is partially open. The cylindri- 
cal portion of the valve protects the 
valve-seat and the valve-face so that 
the valve may remain tight when closed. 

Steam-traps. — The object of a 
steam-trap is to drain condensed water 
from steam-pipes without allowing steam FlG - 99- 

to escape. As a rule a trap is placed below the pipe to be 
drained so that the drip from the pipe will run into it. Some 
traps that return the condensed water to the boiler do not 
conform to this rule. 

Some traps, such as the McDaniels, the Baird, and the 
Walworth, have a valve under the control of a float, which 
will allow water to pass but not steam. 

A 





Fig. 100. 

The McDaniels trap is shown by Fig. 100. The drip 

enters at C and escapes through the exit at E when the valve 

G is open. This valve is raised by the spherical float when 

the water rises to a sufficient height. When the water is 



258 



S TEA M-B OILERS. 



drained from the pipe served by the trap, the water-level in 
the trap falls and the valve G is closed. D is a counter 
weight to balance the weight of the spherical float. The 
valve at G can be opened by screwing down the screw at A 




Fig. 102. 
on to the counterweight. The trap can be emptied through 
the valve at F. 

The Baird trap, Fig. 101, has a spherical float D which 
controls a piston-valve at J. The inlet is at C, and the outlet 



BOILER A CCESSORIES. 



259 




at /. The screws A and B allow the valve J to be opened or 
closed by hand. 

The Walworth trap (Fig. 102) has a floating bucket into 
which the drip overflows after the outer case is partially 
filled. When the bucket sinks it opens a passage through 
the central spindle, and the water in the bucket is driven out 
through this spindle. The hand-wheel and screw at the top 
control a valve which is closed when the trap is working. 

The Flynn trap (Fig. 103) depends for its action on a head 
of water acting on a flexible diaphragm. Water may enter 
at the top or the bottom at ori- 
fices marked A. It fills the pipe 
B and the globe C as high as 
the end of the pipe E, and pro- 
duces a pressure of about a 
pound per square inch on the 
under side of the diaphragm at 
D. The spring at G produces 
a pressure of about half a pound 
per square inch on the upper 
side of the diaphragm. Conse- 
quently the valve leading from 
the chamber F to the escape- 
pipe H is closed so long as the 
pipe E remains empty. But 
when the water overflows the 
top of the pipe E and fills the 
chamber F, the water-pressure 
on top of the diaphragm will be 
the same as that on the bottom, 
and the spring at G will open 
the valve and allow water to 
escape. If the supply of water Fig. 103. 

at A ceases, the pipe E will be emptied and the valve will be 
closed under the influence of the pressure on the under side 




260 



S TEA M-B OILERS. 




OUTLET 
Fig. 104. 



of the diaphragm. In the trap as actually constructed the 

pipe H is about 24 inches long, in 
the figure it is made shorter in 
proportion. 

The Curtis trap (Fig. 104) has 
an expansion-chamber at C which 
M inlet is closed by a diaphragm A at the 
bottom, and is filled with a very 
volatile fluid. So long as the ex- 
pansion-chamber is immersed in 
water the pressure of the fluid on 
the diaphragm is balanced by the 
spring on the valve-spindle B. If 
the water is drained away and the 
chamber is exposed to the temper- 
ature of steam (212 F. or more), the fluid vaporizes and 

exerts enough pressure on the diaphragm to compress the 

spring and close the exit-valve. 

Return Steam-trap. — The traps thus far considered usu- 
ally discharge against the pressure of the atmosphere. They 

may discharge into a closed tank 

against a pressure that is higher 

than the atmosphere, but in all 

cases the pressure in the pipes 

drained by the trap must be 

higher than the discharge-pressure. 

Return steam-traps are arranged 

to discharge directly into the 

boiler. 

The Bundy return-trap, shown 

by Figs. 105 and 106, is set three 

feet or more above the water- 



line in the boiler. 



It 



is so 




105. 



made that it is first opened to the pipe to be drained, and fills 
up under the pressure in that pipe. It is then put in commu- 



BOILER ACCESSORIES. 26 1 

nication with the steam-space and with the water-space of 
the boiler, and the water previously collected drains into the 
boiler. 

The trap consists of a pear-shaped receptacle or closed 
bowl, hung on trunnions, through which the bowl is filled and 
emptied. When empty the bowl is raised by a weight and 
lever; when filled with water it overbalances the weight and 




Fig. 106. 

falls. The ring around the bowl limits the motion. The 
condensed water from the pipe or system of pipes to be 
drained enters the trap through the check-valve B, which pre- 
vents water from flowing back from the trap into the pipe to 
be drained. The trap is emptied through the check-valve A, 
which prevents water from the boiler from flowing into the 
trap. At C is a valve under the control of the trap, which 
receives steam by a special pipe from the boiler. When the 
trap is empty and is lifted by the weight and lever, the valve 
C is thrown down and is shut; water then flows in through 
the valve B from the pipe to be drained, and air escapes from 
an air-valve below C, which is open in this position of the 
trap. A check-valve on the air-pipe prevents air from en- 



262 



S TEA M-BOILERS. 



tering the trap if a vacuum happens to be formed in it. When 
the bowl is filled it falls and opens the steam-valve C, and 
steam enters the bowl through a curved pipe shown in Fig. 
1 06. The pressure in the bowl is now equal to that in the 
boiler, and the water collected flows into the boiler by gravity. 
Separators. — If steam is carried to a distance in pipes, a 
^^^mm^H considerable amount of water of conden. 

1^" ,<-,=--— ---iszzp. sation accumulates. It is undesirable to 
have this water delivered to a steam- 
engine in any case, but if the water ac- 
cumulates in a pocket or a sag in the 
piping, it may come along with the steam 
in a body whenever there is a sudden 
change of steam-pressure, and then the 
engine will be in danger of injury. 

A good way of removing such water 
is to allow the steam to come to rest 
in a steam-drum of suitable size, from 
which the water is drained by a steam- 
trap ; the steam meanwhile may flow from 
a pipe at the top of the drum. A small 
steam-drum used as separator is likely 
to fail, from the fact that the steam does 
not come to rest, or because the entering 
and leaving currents of steam are not 
properly separated. 

The Stratton separator, shown by 

Fig. 107, brings in the steam at one side 

of a cylinder, with a whirling motion 

Fig. 107. * that throws the water onto the side of 

the cylinder; dry steam escapes through a pipe in the middle. 

A good steam-separator will remove all but one or two 

per cent of moisture from steam, even though the entering 

steam is very wet. 

Attention has already been called to the use of separators 




BOILER A CCESSORIES. 



263 



with some forms of water-tube boilers which do not have a 
sufficient free water-surface for the disengagement of steam. 
Feed-water Heaters. — The feed-water supplied to a boiler 

SAFETY 
VALVE 



BLOW -OFF 



* FEED TO 

BOILER 



EXHAUST 




FEED FROM 
PUMP 



a^^^^^SSSOTS^iglgSS 



u 

MUD BLOW-OFF 

Fig. 108. 
may be heated up to the temperature of the exhaust-steam by 
passing it through a feed-water heater. Feed-water heaters 
are sometimes made open, i.e., the steam from the engine 



264 



S TEA M-BOIL ERS. 



mingles with and heats the feed-water. Such heaters have 
the disadvantage that the oil from the engine is carried into 
the boiler. 

A closed feed-water heater resembles a surface condenser, 
and as the steam and water do not mingle, there is no danger 
of carrying oil from the engine into the boiler. The Wain- 
wright heater, shown by Fig. 108, has the heating-surface of 
corrugated copper or brass tubes, of peculiar make, to allow 
for expansion. The steam from the engine passes around 
the tubes and the feed-water passes through the tubes. 

The Berry man feed- water heater, shown by Fig. 109, is 
arranged to have the exhaust-steam pass 
through a series of inverted U tubes, 
around which the feed-water circulates. 
Live-steam feed-water heaters take 
steam from the boiler to raise the tem- 
perature of the feed-water up to, or 
nearly to, the temperature in the boiler. 
The principal advantage appears to be 
that unequal contraction, due to the in- 
troduction of cold water, is avoided. It 
is claimed that with some forms of 
boilers a better circulation is obtained 
by aid of such a heater. 

The use of a feed-water heater for 
removing lime-salts from feed-water has 
been discussed on page 73, and an ex. 
ample of such a feed-water heater was 
illustrated in connection therewith. 

Feed-pipes. — The temperature of 
the feed-water is usually much below 
the temperature in the boiler. It thus 
mud pipe becomes essential to so locate the inlet, 

FlG - io 9- and to so distribute the water, that un- 

due local contractions may not occur; this is of special im- 




BOILER ACCESSORIES. 265 

portance when the supply is intermittent. The feed-pipe for 
the cylindrical tubular boiler, shown by Plate I, enters che shell 
near the water-line, through the front head. It is carried 
along one side of the boiler for about three fourths of its length, 
and then is carried across over the tubes and opens downward. 
A feed-pipe is often perforated to give a better distribution of 
the feed-water. 

The shell is reinforced by a piece of plate riveted on the 
outside, where the feed-pipe enters the boiler. The end of 
the pipe has a long thread cut on it, so that it can be secured 
through the reinforcing-plate and the boiler-shell, and may 
then receive a pipe-coupling which connects it to the continu- 
ation of the feed-pipe inside. 

Sometimes the feed-water is delivered to an open trough 
inside the boiler, from which it overflows in a thin sheet. 
Or a perforated pipe may deliver the water in form of spray 
in the steam-space. Either method has the advantage that the 
water comes in contact with stenm and is heated before it 
mingles with the water in the boiler. There is the disadvan- 
tage that the steam-pressure may fall off when the feed-water 
is turned on or is increased. 

It has already been pointed out that the feed-pipe should 
have a globe valve near the boiler, and a check-valve between 
the globe valve and the feed-pump. 

Feed-pumps. — Boilers are commonly fed by a small direct- 
acting steam-pump placed in the boiler-room. The steam- 
consumption per horse-power per hour of such pumps is very 
large, and yet the total steam used is insignificant. They are 
cheap and effective, and easily reguiated. 

Power pumps driven from a large engine are more econom- 
ical, provided their speed can be regulated; they not infre- 
quently are arranged to pump a larger quantity than required 
for feeding the boiler, the excess being allowed to flow back to 
the suction side of the pump through a relief-valve. 

When one pump supplies several boilers, a series of diffi- 



266 STEAM-BOILERS. 

culties is liable to arise. First, if the boilers are fed singly 
in rotation, the krge intermittent supply of feed-water is 
likely to give rise to local contraction and the water-level in 
the boiler fluctuates; there is liability that the water-level will 
fall too low, endangering the heating-surface, or there may be 
excessive priming when the water-level is high. It appears 
advisable that the feed should be delivered to all the boilers 
simultaneously, the supply to each boiler being regulated by 
its stop-valve; each branch pipe to a particular boiler should 
be provided with its own check-valve, and the water-level and 
rate of feeding of each boiler must be carefully watched by 
the fireman, or by a water-tender if there are many boilers. 

An injector is conveniently used for feeding a boiler if the 
feed-water is not too hot; it has the incidental advantage that 
it heats the water as it feeds it into the boiler. An injector 
should be connected up with unions, so that it may readily 
be taken down for inspection. At sea an injector is com- 
monly used when the boilers are fed from the sea or from a 
supply-tank. 

Every boiler should have two independent sources of sup- 
ply of feed-water, so that there may be some resource if the 
usual supply gives out. There may be two pumps, or a pump 
and an injector. A locomotive usually has two injectors. 

Blow-off Pipe. — The blow-off pipe draws from the lowest 
part of the boiler, or from some place where sediment may be 
expected to collect. On the blow-off pipe there is a cock or 
a valve which is opened to blow out water from the boiler. 
Sometimes there are both a cock and a valve. A cock has 
the disadvantage that it may give trouble by sticking; a valve 
may leak and the leak may not be detected. 

The pipe should be carried beyond the cock, so that the 
attendant is not liable to be splashed with hot water, but the 
pipe should end in the boiler-room or where discharge through 
the pipe on account of a leaky cock or valve may be sure to 



BOILER ACCESSORIES. 26/ 

attract attention. Each individual boiler should have its own 
blow-off pipe. 

The blow-off pipe where it passes through the back con- 
nection is covered with magnesia, asbestos, or fire-brick. In 
spite of this protection the blow-off pipe may burn off. The 
device shown by Fig. 1 10 is used to overcome this difficulty. 



WATER LINE 



^ 



Fig. i io. 

When the blow-off cock is shut and the valve on the vertical 
branch is open, there is a continuous circulation of water 
which keeps the pipe from burning. The valve on the verti- 
cal branch is closed before the blow-off cock is opened. 

If a blow-off pipe burns off and water begins to escape, the 
feed-pump should be run at lull capacity to keep water in the 
boiler and guard the piates from burning, if that is possible. 
The fire should then be checked by throwing on wet ashes or 
by other means, unless escape of steam from the break in the 
blow-off pipe prevents. 

Piping to carry steam from a boiler to an engine, for 
heating buildings, and for other purposes is too important to 
be considered as accessory to the boiler. A lew remarks, how- 
ever, may not be out of place- 



^68 STEAM-BOILERS. 

The expansion of the pipe due to changes of temperature 
should be provided for, or else cracks in the pipe or fittings, or 
leakage at the joints may be expected. A common way of 
allowing for expansion is illustrated by Fig. m, which shows 



o 




n 



Fig. hi. 

the connection from a boiler to the main steam-pipe. When 
the main steam-pipe expands or contracts, the short nipple 
between it and the angle-valve turns a little at one or at both 
ends; in like manner the vertical pipe turns a little at the 
nozzle or at the elbow. The motion is so small and so dis- 
tributed as not to give any trouble unless the expansion to be 
provided for is very large. A large and long straight steam- 
pipe may require an expansion-joint. A slip-joint may be 
made of a brass pipe inside a shell with packing-box and fol- 
lower, arranged something like the piston-rod of an engine. 
It is essential that the slip-joint shall be in line or it will be 
cramped and give trouble. For this purpose the ioint may be 
carried and guided by a cast-iron bed-piate. 

Fig. in is so arranged that there is no space where water 
can collect when the boiler is shut off from the main steam- 
pipe. If the stop-valve were in the vertical pipe, as is some- 
times the case, then the pipe over the valve would fill up with 
water when the boiler is shut off, and that water would be 



BOILER ACCESSORIES. 269 

£uddenly blown into the steam-main when the stop-vaive is 
next opened. A pipe so situated should always have a drip- 
pipe to draw off condensed water before the valve is opened. 
As a special example we may mention the pipe leading to an 
engine, which always has a drip-pipe above the throttle-valve. 
Pipes that are likely to be troubled by condensation should 
be continuously drained by a steam-trap. 

Horizontal pipes are sometimes arranged so that water may 
collect in them, due to a sag in the pipe or to the fact that 
they do not properly drain through a side branch. Though 
the water may lie quiet in such a pocket while the draught of 
steam is steady, a sudden increase in the velocity of the steam, 
or a rapid opening of the valve supplying steam to the pipe, 
will sweep the water up and carry it along with the steam. The 
danger from the inrush of water to an engine is readily seen, 
but it is not so well known that the water thus violently thrown 
against elbows and other fittings give rise to leaks, if it does not 
burst the fittings. It is to be remembered that steam offers 
little or no resistance to the movement of water in a pipe, as it 
is readily condensed either from a slight increase of pressure 
or by mingling with colder water. Again, water at the temper- 
ature corresponding with the pressure easily separates, forming 
bubbles of steam, which as easily collapse, and the shock of 
impact of the water gives rise to pressures that search out 
all weak places in the pipe, even at some distance. 

Drawings for piping commonly represent the work as 
though it were all in one plane. There is little liability of 
confusion since the actual piping could usually be swung 
into one plane, turning in tees and elbows and other fittings. 
Lengths are given from centre to centre of pipes represented, 
because the fittings may differ in length. 

Piping up to two inches in diameter can be cut by hand. 
Larger sizes are cut by machine. Sizes of pipe are named 
by the inside diameter; but the actual diameter, especially 
of small sizes, may be larger than the nominal diameter. 



2^0 



S TEA M- BOILERS. 



Pipe sizes are 1, \, f, J, |, I, ij, i£, 2, 2J, 3, 3J, 4, 5, 6, 7, 8, 
10, 12, etc. Brass piping is nearer the nominal size than 
iron piping. Boiler-tubes are named from the outside di- 
ameter. 

Pipe-hangers.— When a pipe needs support it is commonly 
hung from an overhead beam by a wrought-iron ring, a little 




Fig. 112. 



larger than the pipe, which is held up by a lag-screw in the 
beam. If the pipe is long, the expansion is likely to cramp 
the ring on the pipe and then bring an awkward side strain 
on the lag-hook ; or it the hook is open in the direction of 
the expansion, the ring may be lifted out of the hook and so 
the support at that point may be lost. The hanger shown 
by Fig. 1 12 has the supporting ring carried by a roller. The 
track for the roller is carried by lag-screws. In some cases 
the lag-screws can be advantageously replaced by bolts which 
pass clear through the beam. Various modifications of this 
device may be used. For example, the pipe may rest on a 



BOILER ACCESSORIES. 2J I 

toller with a hollow face , the roller is on a horizontal bolt 
which is supported by straps co an overhead beam. 

Area of Steam-pipe. — In order that the loss of pressure 
in a steam-pipe due to friction may not be excessive, it is 
customary to limit the velocity to 5000 or 6000 feet per min- 
ute. If there are many bends or elbows in the pipe, the 
velocity may be 4800 feet per minute, or less. 

Example. — Required the diameter of the main steam-pipe 
leading from a battery of boilers having an aggregate of 3000 
boiler horse-power. Assume the pressure to be 100 pounds 
by the gauge, or about 115 pounds absolute. Assume also 
that a boiler horse-power is equivalent to 30 pounds of steam 
per hour. Then the steam drawn from the boiler in one hour 
is 

30 X 3000 = 90,000 

pounds. The steam per minute is consequently 1500 pounds. 
Now one pound of steam at 1 1 5 pounds absolute has a 
volume of 3.862 cubic feet. Consequently 

1500 X 3.862 = 5793 

cubic feet of steam per minute must pass through the steam- 
main. With a velocity of 5000 feet per minute the area of 
the pipe must be 

5793 -5- 5000=: 1. 157 

square feet, or 166.6 square inches. The corresponding 
diameter is 14J inches. The next larger size of pipe is 16 
inches, which will be used. 



CHAPTER IX, 
SHOP-PRACTICE. 

THE method of work in a boiler-shop depends on the size 
and arrangement of the shop and on the class of work. 
There are, however, certain general principles which can be 
recognized in all modern shops. 

The materials, especially the plates, are received at one 
end of the shop, near which is a storeroom, and a bench for 
laying out work. The plates, after they are laid out, pass in 
succession to the several machines, where they are sheared, 
punched or drilled, planed, rolled, and riveted. The machines 
for performing these operations are arranged in order with 
proper spaces for handling and working. Space is provided 
where boilers may be assembled and receive their tubes and 
furnaces. Machines which, like the punch, have much work 
to do, compared with other machines, may be duplicated. 

There should be an efficient system for handling the 
material at the machines and for passing it on from one 
machine to the next. A good arrangement is to have a 
swing-crane near each machine ; the spaces served by the 
several cranes overlap, so that one crane takes material from the 
next, and so on. It is advantageous, especially in large shops, 
to have a travelling crane that can handle the largest boiler 
made, and which can serve any part of the shop. 

Flanging and smithing are usually done in a separate shop 
or room. A few machine-tools are needed for doing work on 
steam-nozzles, manhole rings and covers, etc. 

A boiler-shop will have an office, a drawing-room, and a 

272 



SHOP-PR A C TICE. 273 

pattern-room, also a storeroom for patterns. These may be 
conveniently located in the second story. 

A Boiler-shop. — The application of the general princi- 
ples just stated and the explanation of details can be best 
given by aid of an example. A medium-size shop for making 
cylindrical boilers has been chosen for this purpose; the 
shop is capable of making any shell boiler of moderate size. 
This shop will employ sixty or seventy men and can turn out 
two 100-horse-power boilers per day. It will take about 
three days to finish one boiler, so that there may be six or 
more boilers in process of construction at one time. 

The shop which is represented by Fig. 113 has one end 
on the street and has a driveway or yard at one side. Plates 
are received at the street-door by a travelling crane and stored 
near at hand. The same crane takes plates to the laying-out 
bench and from there to the crane which serves the shearing- 
machine. Along one side of the shop are arranged in suc- 
cession a shearing-machine, two punches, a plate-planer, a 
set of plate-rolls, and a riveting-machine. Between the 
punches and nearer the wall is a flange-punch ; near the 
planer is a forge for scarfing. This series of machines is 
served by four swing-cranes, and there are also two hydraulic 
cranes near the riveting-machine. These cranes, which are at 
the top of a tower thirty feet high, are operated from the 
working platform of the riveter. There are two shipping- 
doors where the finished boilers are delivered to teams, and at 
each door there is a jib-crane for handling the boilers. These 
jib-cranes and the hydraulic cranes at the riveter have a 
capacity of eight or ten tons ; the swing-cranes may be much 
lighter. A shop where large marine boilers are made will 
have more powerful cranes. 

The machine-shop is near the receiving-door. Here are 
the lathes, planers, and drills for doing work on manholes, 
nozzles, and other fittings ; also a bench for fitting up boiler- 
fronts. Two drills for boring tube-holes in tube-plates, and 



274 



S TEA M-B OIL ERS. 




CO 



2 £ 



133U1S 



SHOP-PR A C TICE. 2 ? 5 

a boring-mill for facing off the flanges of boiler-heads, are 
placed in the entrance to the machine-shop, where work can 
be conveniently brought to them from the boiler-shop. At 
the end partition of the machine-shop are places for storing 
boiler-front castings and sheet-iron. The corner of the boiler- 
shop near the machine-shop is known as the cold-iron shop ; 
here the uptakes, flues, and dampers are made. This shop 
has a shearing-machine, three punches, and a set of rolls 
suitable for. sheet-iron work; also a bench with hand-vises. 

At the rear of the boiler-shop there is in one corner a store- 
room for tubes, stay-rods, channel-bars, and finished fittings. 
In the opposite corner are the forge-shop and the engine- 
room. These are separated from each other and from the 
boiler-shop by glass partitions which do not cut off the light, 
and yet keep the smoke and dust from the forge out of the 
other rooms. 

The main line of shafting is near the wall over the shear- 
ing-machine, punches, and rolls. The shafting for the ma- 
chine-shop and cold-iron shop is driven by a belt from the 
main shaft, near the front end of the building. A space is 
left near the riveter where the plates from the rolls can be 
assembled and bolted together before going to the riveter. 
In front of the riveter there is a space about 60 feet wide 
and 120 feet long where boilers are deposited after leaving 
the riveter. Here the boilers receive their stays and tubes, 
here they are calked and receive ail fixtures that are perma- 
nently attached to the shell. At this place the boilers are 
tested by hydraulic pressure, usually to one and a half times 
the working pressure. When complete the boilers are painted 
and oiled, ready for shipment. 

To illustrate the method of building a boiler more in 
detail, the different steps in making a horizontal boiler will 
be followed in order. 

Flanging Heads. — Regular sizes of boiler-heads flanged 
at one operation by machinery can now be bought on the 



2 j6 S TEA M-B OILERS. 

market, and all except the largest shops are in the habit of 
buying them. The flanging-machine has a former and a die 
between which the plate is formed under hydraulic pressure 
while at the proper flanging temperature. No strains due to 
unequal heating or cooling are set up in this process, and 
the plate, which is allowed to cool gradually, does not need 
to be annealed. 

Irregular sizes and shapes are made in the shop on a 
special cast-iron anvil, which is about six inches deep, flat on 
top, and curved at one side to about the radius of the head to 
be flanged. The corner of the anvil or former is rounded so 
as not to cut the plate. It is placed near a special low forge 
where the plate is heated. 

In flanging, the plate is first marked at short distances on 
the inner circle of the bend with a prick-punch. A portion 
of the plate is then heated to a good heat, and the plate is 
taken to the anvil or former. After adjusting so that the 
depth of flange overhangs the right distance from the edge 
of the former, the heated portion of the plate is beaten down 




Fig. 114. — Lifting-dogs. 

against the side of the former by wooden mauls and then 
smoothed with a flatter and sledge. The plate is then heated 
in a new place and another portion bent. To straighten the 
head and also to remove the strains set up by this way of 
flanging, it should be heated to a dull red and allowed to cool 
gradually. 

The lifting-dogs represented by Fig. 1 14 are used in lift- 



SHOP-PRACTICE. 2J? 

ing and placing the head during the flanging, and in handling 
plates during other operations. 

Fig. 115 represents crane-lifts which are used when plates 
are lifted and carried by cranes. 




Fig. 115. 

After the head is flanged, holes for rivets, stay-rivets, 
and tubes are marked, and all the rivet-holes are punched. 

Flange-punch. — The holes in the flange are punched by 
a special machine shown by Fig. 116. The punch is carried 




by a horizontal wrought-iron plunger which is operated by a 
cam. The die is carried by a hooked extension of the frame. 
The head is held horizontal with the flange down ; the flange 
is dropped between the punch and the die and the lever is 



STEAM-BOILERS. 




Fig. 117. 



pulled to throw the cam into play ; the plunger then makes 
a stroke and punches a hole. The machine is driven by a 
belt, with a fast-and-loose pulley. On the shaft with these 
pulleys is a heavy fly-wheel. A pinion and spur-gear give a 
slow powerful stroke to the gear which moves the cam. 

Punch and Holder. — The punch (Fig. 117) is made of a 
solid piece of tool-steel. It has a flat head and a conical 

shoulder by which it is held onto 
the plunger, a short straight body, 
and a slightly coned point. The 
point is larger at the cutting edge 
than back toward the straight 
body, to avoid friction in the hole. 
A tit in the middle of the face of 
the punch catches in the centre- 
punch mark and centres the hole punched. 

The holder is made of wrought iron. It screws onto the 
end of the plunger, grips the punch by the conical shoulder 
on its head, and draws it down firmly against the plunger. 
Tube-holes. — There are two ways of cutting the holes 
for the tubes in boiler-heads. Some- 
times a small hole is punched at the 
centre of the hole. A tool like that 
shown by Fig. 118 is then put in the 
drill-press. The post in the middle is 
run through the small hole previously 
punched or drilled, and the two cutters 
rapidly cut out the tube-hole to the 
proper size. 

The other way is to 
punch the tube-holes 
at once to the proper 
size by a helical punch 
shown by Fig. 119. The die is made in the form of a ring 
with a flat face, so that the punch begins to cut at the cor- 



~\J 



Fig, 118. 




SHOP-PR A C TICE. 2 79 

ners, and the metal is removed by a shearing cut. Though 
not always done, the holes ought to be punched a little under 
size and then reamed out to give a fair surface against which 
the tubes may be expanded. 

Finishing the Flange. — The boiler-heads are placed on 
the platen of a boring-mill like that shown by Fig. 120, and 
the edge of the flange is turned off. The heads of marine 
boilers are often turned to a true cylinder at the flange to insure 
that they shall exactly fit the cylindrical shell into which 
they are riveted. This also gives a good surface to calk 
against. 

Boring-mill. — A simpler machine than the boring-mill 
shown by Fig. 120 would answer to turn off the flanges of 
the boiler-heads. But the machine is useful in other ways 
and may do the work which is commonly done on a large 
lathe. 

The platen is driven much in the same manner as the 
head of a lathe, through gearing and cone pulleys, to provide 
for various speeds. This gearing is not well shown in the 
figure, as it is hidden by the frame. The cutting-tool is ad- 
justed and controlled much like the tool of a planer. The 
tool-carriage is on a horizontal cross-head which is supported 
at the side frame and on a round vertical bar at the middle. 
The tool can be traversed in and out on the cross-head, and 
the cross-head may be raised or lowered. 

For doing some classes of work the cross-head may be 
set vertically on the guides that are shown on the horizontal 
bars of the frame near the right-hand end. Or, again, a tool 
may be carried by the central rod, which can be fed down by 
the screw at the top. 

Laying on the Plates.— The first and one of the most 
important steps in the work on the shell is the marking out 
of the plates. Generally one man in each shop does all the 
laying out. After squaring the sheet, he marks off the 
length and locates the rivet-holes by means of gauges. These 



28o 



S TEA M-B OILERS, 



gauges have to be made by trial, a suitable allowance being 
made in them on account of the thickness of the plate for the 




Fig. 120. 
change in length due to rolling. There is a gauge for each 
course, or a set of gauges for each size boiler, and also sets 



SHOP-PRACTICE. 



28l 



for the same size, but with different thickness of shell. The 
plates are marked either with a piece of soapstone or with a 
slate-pencil. Rivet-holes are prick-punched at the centre. 
Shearing. — When the plate is laid out it is taken from 




Fig. 121. 

the bench to the shears and any superfluous stock is cut off. 
A shearing-machine is shown by Fig. 12 1. The lower knife 
is fixed and the upper knife is moved by an eccentric inside 
the head. The eccentric-shaft is coupled to the gear-shaft 
by a clutch that is controlled by a treadle. The weight of the 
sliding-head is counterbalanced by a weight and lever at the 
top. Lugs are shown on the casting near the knives ; when 
the machine is required to do extra-heavy work, wrought-iron 
"bolts are put through the lugs and screwed up to strengthen 
the frame. 

The machine is driven by a belt with a fast-and-loose pul- 
ley ; the shaft carrying these pulleys has a pinion gearing into 
a large gear to give the necessary power for shearing. A fly- 
wheel steadies the motion of the machine; it must be able to 
supply the power for shearing-plates without a large reduction 
in speed. 



282 s TEA M-B OILERS. 

Punch. — After the plate is sheared to size it is taken to 
one of the punches and all the rivet-holes are punched. Larger 
openings for man-holes and other fittings are cut out by punch- 
ing overlapping holes, thus leaving a ragged edge which is 
afterwards chipped smooth. The plate is not entirely cut away 
at such large openings, but the piece to be removed is left 
hanging at three or four places until after the plates are rolled 
into cylindrical form. If the pieces were removed, there would 
be less resistance to the rolls at such places and the plates 
would have a conical form instead of a true cylindrical form. 

The punches resemble the shears shown by Fig. 120, with 
a punch and die instead of the knives. Machines are often so 
made that they either punch or shear. 

Planing. — After the plate is sheared and punched the 
edges are planed to a slight angle to give a good calking 
edge. 

The planer shown by Fig. 122 has a long narrow bed on 
which the edge of the plate is laid and to which it is clamped 
by a follower; the follower is forced down by screws which 
pass through a beam as shown. The tool-carriage is drawn- 
back and forth by a leading-screw; the tool is made to cut on 
both strokes, and is fed by hand between the cuts. 

Scarfing. — When the plates are joined by a lap-joint the 
proper corners of each plate are heated in a portable forge 
near the planer, and are drawn down or scarfed so that the 
overlapping plates may come close together and not leave a 
space. 

Plate-rolls. — The plates for forming the cylindrical shell 
are bent to shape cold by running them through bending-rolls 
The horizontal roll represented by Fig. 123 has two parallel 
rolls below that are driven in the same direction by gearing. 
The upper roll is adjusted at each end separately, and some 
care is required or the shell will receive a conical shape instead 
of a true cylindrical shape. The bearing at one end of the 



SHOP-PRACTICE. 



283 




284 



S TEA M-B OILERS. 



roll can be swung out, as shown by the figure, to remove the 
plate after it is rolled. 

The rolls may be driven in either direction by crossed and 
open belts. The plate to be rolled has one edge introduced 




Fig. 124. 

between the upper and lower rolls, the upper roll is brought 
down and the rolls are started up. The plate is run through 
nearly to the other edge then the top roll is screwed down 



SHOP- PR A C TICK. 285 

farther and the rolls are reversed. Thus the plate is run back 
and forth and the todp roll is gradually rawn down till the 
plate acquires the proper form. 

The extreme edges of the plate arc not bent in this process; 
they are commonly bent afterwards by hammering them with 
sledges. Some rolls have a special device for bending the 
edges; it consists of two short overhanging rolls about fifteen 
inches long, one concave and the other convex. The ends of 
the plate are fed through these rolls sideways, and are bent 
before they are introduced into the long rolls. 

Vertical rolls, shown by Fig. 124, are coming into use in 
boiler-shops. They take up less floor-space, and the plate after 
it is rolled up into cylindrical form is easily hoisted off from 
the front roll. For this purpose the front roll is counterbal- 
anced and the top end can be swung out clear from the hous- 
ing. The figure shows the rolls as erected by the builders; 
in the boiler-shop the plate at the lower end of the rolls is 
flush with the floor of the boiler-shop. 

The width of plate that can be rolled by either horizontal 
or vertical rolls depends on the length of the rolls, The 
length of the rolls and the reach of the riveter (to be men- 
tioned later) determine the width of plate that can be handled 
in the shop. 

Assembling and Riveting. — When the plates for a boiler 
have been punched, planed, and rolled they are assembled in 
courses, and bolted together ready for riveting. Formerly 
boilers were commonly punched and riveted ; now it is cus- 
tomary to punch the rivet-holes one eighth of an. inch smaller 
than the finished size and then drill to the right size after the 
boiler is assembled. This is more expeditious than drilling 
directly, and as all the metal affected by punching is removed 
it gives as good results. It is the custom in most shops to 
drill the holes out at the riveting-machine immediately before 
the rivets are driven and thus each rivet-hole is sure to be 
true. 



286 S TEA M-B OILERS. 

The shells of heavy marine boilers are drilled after the 
plates are assembled without previous punching. A few holes 
are drilled before the plates are rolled and serve for bolting 
the plates in place when the boiler is assembled. There are 
two forms of machines for drilling marine-boiler shells. In one 
the boiler is placed horizontal on rollers so that it may be 
readily turned, There are two or three upright frames each 
carrying a drill. The frames may be adjusted lengthwise of 
the boiler, and the drills may be set at any height or turned at 
an angle. When a longitudinal seam is drilled the boiler is 
rotated to bring a row of rivets to a drill, and the frame is trav- 
ersed from hole to hole. When a ring-seam is drilled the 
drill is brought to the proper place, and the boiler is rotated so 
as to bring the rivet-holes in succession to the drill. The 
other machine has the boiler placed on one end and the verti- 
cal frames carrying the drills can be rotated into place, and the 
boiler can be turned on a vertical axis. 

If plates are punched and riveted without drilling, the 
holes should be punched from the side of the plate which 
comes in contact with the other plate. The reason for this 
is that the die is always a little larger than the punch and the 
hole is slightly conical, larger at the side where the die holds 
up the plate. If the smaller ends of the holes in two plates 
are brought together, then the rivet fills the hole better and 
draws the plates up more perfectly as the rivet cools. It is 
clear that three or more overlapping plates should always be 
drilled, as punched holes cannot always be brought together in 
a proper manner. This is aside from the desirability of drill- 
ing all rivet-holes. 

Returning now to the assembling of a cylindrical boiler, 
the process is as follows: The back head is put in the rear 
course or ring of the shell, and is bolted with six or eight bolts 
through the punched holes. The head and ring are hoisted 
up to the drill near the riveter, and six or eight holes are 
drilled at about equal distances around the seam holding the 



SHOP-PRACTICE. 287 

head into the ring or course, and rivets are driven by the 
machine in these holes. The bolts are now taken from the 
punched holes, and all the remaining holes are drilled and 
riveted, completing the ring-seam through the flange of the 
back head. The reason for driving a few rivets first, at equal 
intervals, is that the errors of spacing, when any exist, are 
distributed, and are removed during the subsequent drilling; 
while such errors might accumulate and give trouble if the 
seam were riveted in succession beginning at one point, 
without first driving a few rivets at intervals. 

After the ring-seam through the flange of the head is 
completed, the longitudinal seam or seams are drilled and 
riveted. Here again a few rivets are driven at intervals 
before the seam is riveted up. A few holes at the ends of 
the seams are left for convenience in joining onto the next 
course. 

The head and first course are now lowered onto the next 
course, which has been assembled in readiness. A few bolts 
are put through the punched holes, and the two courses are 
hoisted up, drilled and riveted in the way already described 
for the rear course. 

When all the courses are riveted together the front head 
is put in with the flange out so that the rivets in that flange 
can be driven on the machine. The closing seams on a boiler 
which, like the Scotch boiler, has both heads set with the 
flange in, must be riveted by hand. 

Rivets are heated in a small forge near the riveter and 
are passed to a man inside the boiler, who picks them up in 
tongs, thrusts them through the holes from within and guides 
the head of a rivet up to the die which is inside the boiler. 
Sometimes the rivets are thrust through from without, in 
which case the man inside the boiler guides the point to the 
die. On the platform of the machine stand the riveter and 
two or three helpers. They adjust the boiler so that the 
rivet is brought between the dies, and the riveter pulls the 



288 STEAM-BOILERS. 

lever which controls the ram, and the outer die is driven 
against the rivet, forming the head and closing up the rivet 
in the joint. 

The holes are drilled about one sixteenth of an inch larger 
than the rivets. The pressure of the dies varies from 20 to 
70 tons, depending on the thickness of the plate ; enough to 
compress the rivet and fill the hole completely. The rivets, 
as they cool, shrink and draw the plates firmly together. 

Riveting-machines. — There are four types of riveting- 
machines used for boiler-work, depending on the method of 
moving the ram or plunger which carries the movable die. 
The motion may be derived from — 

1. A cam and toggle. 

2. A hydraulic cylinder, 

3. A combination of a hydraulic cylinder with a cam and 
toggle. 

4. A steam-cylinder. 

The cam a?id toggle riveter is now seldom used. In it 
the ram carrying the movable die is driven by a toggle-joint 
that is closed by a cam, which in turn is driven by a belt and 
gearing. The adjustment for different thicknesses of plate is 
made by a wedge behind the ram, which can be set by aid of 
a screw. The pressure on the rivet is controlled by the elas- 
ticity of the frame of the machine and the setting of the 
wedge ; it cannot be regulated satisfactorily. 

The hydraulic riveter, in one form or another, is most com- 
monly used at the present time. With it a definite pressure 
can be applied to each rivet whatever the thickness of plate. 
Fig. 125 represents a hydraulic riveter with a reach of 96 
inches which can apply a pressure of 150 tons. It consists 
essentially of two heavy cast-iron levers or beams, bolted 
together near the middle and at the lower end. One beam 
carries the fixed die at its upper end ; the other carries the 
ram and hydraulic cylinder. The stroke of the ram can be 
adjusted and is controlled by a single lever. The ram moves 



SHOP-PRACTICE. 



289 



in straight girders, and may apply an eccentric pressure with- 
rotatin^ or springing. 

Some hydraulic riveters have a hydraulic closing device 




Fig. 125 

for holding the plates together while the rivets are driven. 
Even when furnished it is commonly not used. 

The reach of a riveting-machine is the distance from the 
dies to the bed-plate at the middle of the machine. It limits 
the width of plate that can be riveted by the machine. 

A portable hydraulic riveter is shown by Fig. 126, which 
has a reach of 12 inches and can apply a pressure of 75 tons. 
It can be swung into position by a crane and can be turned to 
any angle by the gear at the trunnion. This type of ma- 
chine is used largely for bridgework ; it is sometimes used 



290 



S TEA M-BOILERS. 



for riveting nozzles, manhole-rings, brackets, and reinforcing- 
plates onto boilers. 

The power for working a hydraulic riveter is derived from 
either a steam-pump or a power-pump. A heavy geared 




power-pump is shown by Fig. 127; it is run continuously 
and delivers water to an accumulator from which water is 
supplied to the hydraulic cylinder which moves the ram. 
The accumulator consists essentially of a loaded piston or 
plunger. Water is pumped into the cylinder of the accu- 
mulator, and is drawn out by the hydraulic cylinder as needed. 
When the accumulator reaches the end of its stroke it closes 



SHOP-PRACTICE. 



! 9 I 



a valve on the pipe from the pump so that it receives no 
more water; at the same time it opens a by-pass from the 
delivery to the suction of the pump which continues to run, 
but has at that time very little resistance to overcome. When 




Fir. 127. 

some water has been withdrawn from the accumulator the by- 
pass is closed and the valve on the delivery-pioe is opened. 
When a steam-pump is used there is a device for shutting off 
steam from the pump when the accumulator is near the end of 
its stroke, and letting it on again when more water is required. 
An accumulator, shown by Fig. 128, is loaded by scrap- 
iron in a plate-iron cylinder. Inside the plate-iron cylinder is 



292 



S TEA M-BOILERS. 



a cast-iron cylinder which is closed at the top and which moves, 
on a fixed plunger. This plunger passes through a stuffing- 
box and is carried by a cast-iron bed-plate. When water is. 




Fig. 128. 
pumped into the cylinder through a passage in the fixed 
plunger, the whole weight of the cylinder, plate-iron casing, 
and scrap-iron load are lifted. The pressure required to da 



SHOP-PR A CTICE. 



293 



this depends on the load; it is the pressure which is exerted 
on the plunger of the hydraulic cylinder moving the ram. 
The frame of I beams at the sides forms a guide for the 
accumulator-cylinder and its load. 

Another form of accumulator, loaded with heavy cast-iron 
blocks and without any exterior guides, is shown by Fig. 1 29. 




Fig. 129. 

The hydraulic riveter with toggle and cam combines the 
simplicity of the cam-and-toggle machine with the advantage 
of a definite and determinable pressure on the rivet, which is 
the best feature of the hydraulic machine. The toggle bears 
against the ram at the front end, and against the plunger of a 
hydraulic cylinder at the back end. The cylinder is connected 
with an accumulator which is loaded to give the desired pres- 
sure on the rivet. Suppose that pressure to be 30 tons; then 



294 



S TEA M-B OILERS. 



when the cam closes the toggle, the rear end, resting against 
the hydraulic plunger, remains at rest, and the front end 
drives the ram and compresses the rivet till a pressure of 30 
tons is reached. When that pressure is reached the hydraulic 
plunger yields, forces water into the accumulator and raises 
the load on it. When the cam releases the toggle, the hy- 
draulic plunger moves forward and the load on the accumula- 
tor falls and drives water into the cylinder. The stroke of 
the hydraulic plunger may be very short, as the principal part 
of the stroke of the ram is made before the piunger yields. 




Fig. 130. 

There is no loss of water except by leakage, which may be 
made up from time to time by a hand-pump. This machine 
gives a definite pressure on the rivet whatever the thickness 
of the plate, like the plain hydraulic riveter. It has no pump 
and the accumulator is smaller. If the plunger has a large 
area, the load on the accumulator need not be very great. 
A steam-riveter, shown by Fig. 130, has the same exter- 



SHOP-PRACTICE. 295 

nal appearance as a hydraulic riveter, except that the power 
is applied by the direct pressure of steam on a piston, which 
must have a large area to give sufficient pressure to drive the 
rivets properly. The steam-valve is balanced so that it can 
be easily moved by the working- lever. If the valve is opened 
slowly, the ram is first moved forward against the rivet and 
then full pressure is applied to close the joint; but if the 
valve is opened promptly, the ram strikes a blow like that of 
a hammer. There is no reason why this cannot be guarded 
against if the valve is small and the machine is operated care- 
fully. The fact that the machine is commonly so used that 
it strikes a blow, and the fact that it is wasteful of steam, have 
brought the steam-riveter into disrepute except for small or 
for portable machines. The ram is moved back by the steam 
before escaping, after a rivet is driven. 

Hand-riveting. — In a modern boiler-shop almost all the 
riveting is done by machine because it is cheaper and, espe- 
cially on heavy work, is more likely to be well done. There 
are, however, a good many rivets on any boiler that must be 
driven by hand. In such case the rivet, which may be heated 
entirely or at the point only, is thrust through the hole from 
within and is held up by a man inside, who has for this pur' 
pose a hammer or weight which weighs about 20 pounds on a 
long handle. He has also an iron hook which he hooks into 
a rivet-hole, and against which he gets a purchase to hold the 
rivet up while it is driven. Two men with hammers that 
weigh about 5 pounds drive the rivet, striking in turn. A few 
heavy blows are struck to close the joint and partially form 
the head, then the head is finished in the shape of a straight- 
sided cone with lighter hammers. If the rivet is long enough 
to form a good head, and if it is driven with care and skill, 
hand-riveting may be equal to machine-riveting. If the heads 
are ill-formed, or if they are too low, the work may be very 
inferior. 

Snap-riveting. — This method of riveting, which is espe- 



296 5 TEA M-B OILERS. 

cially convenient ior driving rivets in contracted spaces, has 
some resemblance to machine-riveting. The rivet is thrust 
through the hole and held up from within the boiler. The 
joint is closed and the head is roughly formed by a few blows 
of a heavy hammer, then a snap or die is held on the rivet 
and driven with sledge-hammers. For large rivets the sec- 
tion of the snap should be a parabola, and the head should be 
relatively small in diameter and high, because this form causes 
the rivet to fill the hole better and makes sounder work. 

Tube-expanders.— The tubes are expanded into the tube- 
sheets to make a steam-tight joint, beginning at tne least acces- 
sible end. They are commonly a little too long and are cut 
off at the projecting end by a tube-cutter. The tubes extend 
through the tubes a slight amount, and are beaded over, after 
they are expanded, by a special tool. The expanders most 
commonly used are known as the Prosser and the Dudgeon 
expanders. 

The Prosser expander, represented by Fig. 131, is made up 




ig. 131. 

of a number of steel segments held in place by a spring on a 
cylindrical extension of the segments. The acting part of the 
segments have the form to be given to the tube after it is 
expanded. The inside of the segments forms a straight hol- 
low cone into which a steel taper pin fits. The expander is 
forced into the tube and is expanded by driving in the pin 
with a hammer. This should be done gradually so as not to 
distress the metal of the tube too much, and the expander 
should be frequently slacked back and shifted part way round 
on account of the spaces between tne segments. 



SHOP-PRACTICE. 



297 



The Dudgeon expander, Fig. 132, has a set of rolls, three or 
more, in a frame. The rolls are forced out against the sides 




Fig. 132. 
of the tube by driving in a taper pin. The pin and frame are 
rotated as the pin is driven, and the rolls gradually force the 
tube against the tube-plate. 

Although the two expanders accomplish much the same 
result, the action is different. The Prosser causes an abrupt 





Fig. 133. Fig. 134. 

stretching of the tube and leaves the tube as shown by Fig. 
133, bearing at the corners of the plate only. The Dudgeon 
enlarges the end of the tube and makes it bear against the en- 
tire thickness of the tube-sheet. 

Alter the tubes are expanded the ends are beaded over bv 



298 



STEAM-BOILERS. 



a special tool, as represented in both figures, which adds to 
their grip on the plate when they act as stays. 

A vacuum may possibly be found in a boiler, if it is allowed 
to cool without admitting air. The Prosser method has an 
advantage in such case, when the tubes act as struts between 
the heads. The Dudgeon method will then act by friction 
only. The rollers might be shaped to give an expansion just 
inside the plate, instead of making them straight; there is, 
however, no evidence of trouble from this source in practice. 

Calking. — The riveted seams of a boiler are made steam- 
tight by calking, which consists in driving the lower part of 
the planed edge forcibly against the plate beneath. Fig. 135 
shows the form of calking-tool used in hand-calking, the posi- 




Fig. 135. 

tion in which it is held, and the way the extreme edge of the 
plate is compressed against the plate beneath. The acting sur- 
face of the tool, which is about an inch wide, is ground at an 
angle of somewhat less than 90 , and the edge is rounded 
slightly so that it will not cut the lower plate. The tool is slid 
along the under plate against the edge of the upper plate and 
struck with a hammer. If the tool is ground to a sharp edge 
and used carelessly, a groove may be cut in the under plate 
and serious injury may be done. 

A pneumatic calking-machine or tool is now used for 
doing most of the calking in boiler-shops. In general prin- 
ciple it resembles a rock-drill, and consists of a cylinder in 



SHOP-PR A C TICE. 2 99 

which works a piston and rod on the end of which is the 
calking-tool. Air is supplied for working the piston, at a 
pressure of 60 or 80 pounds, through a flexible tube. It 
makes about 1500 working-strokes a minute, 3/16 of an inch 
long. The calker, which is about 2\ inches in diameter out- 
side and 15 inches long over all, is held by a workman who 
presses it slowly along the seam to be calked. The edge of 
the tool is well rounded so as not to injure the lower plate. 
Work can be done four times as rapidly with the pneumatic 
calker as by hand. 

Cold-water Test. — After the boiler is calked it is tested 
to about once and a half the working pressure, with cold 
water. During the test the boiler is carefully watched to 
detect any notable change of shape or other sign of faulty 
design or construction, and important leaks are marked; 
small leaks are of no consequence, as they will fill up with 
rust. Important leaks must be calked after the pressure is 
relieved ; if necessary, pressure may be applied again to see if 
they are stopped. The method of making this test and the 
precautions to be observed are given on page 224. 

If the boiler is examined by a boiler-inspector, he makes 
his inspection before the boiler is painted, and stamps certain 
letters on the head or over the fire-door to show that the 
boiler has passed inspection. 

Finally the boiler is painted and oiled ready for shipping. 



CHAPTER X. 
BOILER-TESTING. 

The main object of a boiler-test is to determine the 
amount of water evaporated per pound of coal, or, more ex- 
actly, the amount of heat transferred to the boiler per pound 
of coal burned. For this purpose it is necessary to deter- 
mine : 

i. The number of pounds of water pumped into the boiler 
during the test. 

2. The number of pounds of coal burned, and the weight 
of ashes left. 

3. The temperature of the feed-water when it enters the 
boiler. 

4. The pressure of the steam in the boiler. 

5. The per cent of moisture in the steam discharged from 
the boiler. 

It is desirable to determine the conditions of combustion, 
such as the draught, the weight of air supplied per pound of 
coal, the composition of the products of combustion, and the 
temperature of the escaping flue-gases. It is also desirable to 
have determinations made of the composition of the coal and 
its total heat of combustion, but, as was explained in Chapter 
II, these determinations should usually be intrusted to a 
chemist and to a physicist. 

Water. — The best and most satisfactory way is to weigh 
the feed-water directly, in proper tanks or barrels on scales. 
There should be two barrels or tanks large enough so that the 
filling, weighing, and emptying may proceed without haste. 



BOILER- TES TING. 3 O I 

The scales should be adjusted and tested with a standard 
weight and should be known to be correct and sensitive. 
Good commercial platform scales are sufficient for this pur- 
pose. 

The weighing-barrels should be placed high enough to 
discharge into a tank or reservoir from which the feed-water 
is drawn by a pump or injector. This tank should hold more 
than both weighing-barrels, so that when it is about half 
empty an entire barrelful of water may be discharged into it 
without danger of overfilling it and wasting water. The bar- 
rels are emptied through large quick-opening lever- valves; 
this point should receive attention, as any delay caused by 
small valves is vety annoying. 

The weighing-barrels are filled either from a water system 
or by a special pump from a well or reservoir. When a direct- 
acting steam-pump is used, a quarter-inch by-pass should be 
carried from the delivery-pipe to the suction-pipe; the pump 
will then run slowly when the valves on the pipes leading to 
the weighing-barrels are shut ; when one of these valves is 
opened the pump starts away promptly, and it slows down 
again when the valve is shut. If a power-pump is used, it 
may be convenient to arrange so that it shall run all the time 
at full power, discharging into the well or reservoir when 
neither barrel is filling. 

Weighing water, though simple enough, requires care and 
intelligence, as any blunder will spoil the test. The observer 
should proceed systematically. He will naturally start with 
both barrels filled, weighed and recorded before the test 
begins. When the level in the feed-tank has fallen so that it 
can receive a barrelful of water he will open the discharge- 
valve from one barrel, which should be marked and designated 
as Barrel No. i. When that barrel is emptied, he will close 
the valve and weigh the barrel ; the weight empty is set down 
and subtracted from the weight full to get the weight dis- 
charged. The record of weights is kept in a table con- 



302 Sl'EAM-BOILERS. 

taining columns for the name of the barrel, weights full, 
weights empty, weights discharged, and time at which dis- 
charged. The weight of the barrel empty must be taken 
each time, as the barrel will not drain completely in the time 
that can be allowed. 

Water may now be turned on to fill Barrel No. I, and 
Barrel No. 2 may be emptied, as occasion demands. Then 
one barrel may be filling when the other is emptying, and the 
work may proceed rapidly but without confusion. The errors 
that a novice is liable to are either to forget to record the 
weight of a barrelful of water, or to empty a barrel that has 
not been weighed. 

It is convenient and almost necessary to have some sort of 
an index or telltale to show the water-weigher where the 
water-level is in the feed-tank. For this purpose we may use 
a float, with a string that runs up over a pulley and is kept 
taut by a small weight moving over a scale, which is placed 
in front of the weighing-barrels. This float is not used to 
determine the level of the water in the feed-tank at the begin- 
ning and end of the test. 

At the beginning of the test the level of the water in the 
feed-tank is marked, and at the end of the test the level is 
brought to the same mark, so that all the water delivered by 
the weighing-barrels is drawn out of the feed-tank by the 
feed-pump. A good way of marking the water-level is to 
fasten to the side of the tank a piece of wire bent into a hook, 
with its point projecting slightly above the water-level. This 
hook will commonly be placed in position before the test 
begins, and the tank will be filled up to the level so marked 
before water is drawn from the feed-tank. 

If water cannot be weighed directly, it may be measured 
in tanks of known capacity which are alternately filled and 
emptied. Or the water may be measured by a good water- 
meter, which must be tested under the conditions of the test 
to determine its error. Care must be taken to keep the meter 



BOILER- TES TING. 303 

free from air or it will record more than the amount of 
water which actually passes. Boiler-tests on steamships can 
scarcely be made without using meters. 

At the time when the test begins, the water-level is noted 
at the water-glass, and at the end of the test the water-level 
is brought to the same place. The best way is to fix a 
wooden scale near the water-glass and record the height of the 
water above an arbitrary point on the scale. Sometimes a 
string is tied around the glass at the water-level when the test 
is started ; in such case the distance of the string from some 
fixed point on the fittings of the water-glass must be recorded, 
so that the string can be replaced if it happens to be moved 
or if the glass tube breaks. If the water is not brought 
exactly to the same level at the end as at the beginning of the 
test, the difference is noted and allowance is made. It has 
already been pointed out that the apparent height of the 
water depends to a certain extent on the rate of vaporization 
and on the rapidity of circulation in the boiler; consequently 
the boiler must be making steam at the same rate at the times 
when the water-level is observed for beginning and ending the 
test. 

All pipes leading water to or from the boiler, except the 
feed-pipe, must be disconnected. Steam may be taken for 
any purpose and through any pipe, so far as the boiler-test is 
concerned. 

Frequently the steam used by an engine is determined by 
weighing the feed-water for a boiler which is used exclusively 
for that engine. If the boiler is fed by an injector, the steam 
for running the injector should be taken from the boiler, for 
it will be condensed by the feed-water and returned to the 
boiler. A very small amount of the heat (less than two per 
cent) in the steam supplied to an injector is used in pumping 
the feed-water; the remainder is used in heating the feed- 
water and is returned to the boiler. The temperature of the 
feed-water must be taken before it goes to the injector. If the 



304 STEAM-BOILERS. 

boiler is fed by a direct-acting steam-pump, that pump should 
be run with steam taken from some other source. If that 
cannot be done, then the steam used by the pump must be 
determined and allowed for, unless the exhaust from the 
pump can be turned into and condensed by the water in the 
feed-tank, in which case the pump is in the same condition 
as an injector. The best way of determining the amount of 
steam used by a steam-pump is to condense it in a small sur- 
face condenser, and to collect and weigh the condensed water. 
Or the steam may be run into a barrel filled with cold water, 
which is weighed before and after steam is run in. This 
method requires that the barrel shall be emptied when the 
water begins to vaporize, and filled afresh with cold water. 
Steam used by a calorimeter for determining the amount of 
water in steam must be ascertained also; the methods will be 
given in connection with a description of the instruments. 

Coal and Ash. — The coal required during a boiler-test 
should be brought in as required in barrows; it may be fired 
from the barrow or dumped and fired from the floor, 'i ne 
barrow should be weighed full and empty, and the difference 
should be recorded together with the time ; the latter to serve 
as a check on the record and make sure that a barrow-load is 
not neglected. The weight of the barrow is usually the same 
throughout the test. Any coal left unburned is weighed back 

It is essential that the condition of the fire shall be tne 
same at the beginning and at the end of the test. There are 
two methods in vogue for trying to attain this result ; if the 
test is 24 hours long or more, the condition of the fire is esti- 
mated by its appearance; if the test is 10 or 12 hours long, 
the test is started and stopped with the grate empty. These 
are for tests of factory boilers with a combustion of 15 to 20 
pounds of coal per square foot of grate per hour. For tests 
on marine or locomotive boilers, where the rate of combustion 
may be twice or five times as rapid, the duration of a test 
may be correspondingly reduced. 



BOILER- TES TING. 305 

Coal in solid mass will weigh 70 or So pounds to the cubic 
foot; when lying on a grate it will weigh 50 or 60 pounds. 
It is difficult to estimate the thickness of the bed of coal on a 
grate nearer than two inches. But a layer of coal two inches 
thick will weigh 8 or 10 pounds, which is about half the rate 
of combustion for a factory boiler. If a test is only ten hours 
long, the error resulting from a wrong estimate of the thick- 
ness of the fire may readily be five per cent. If the test lasts 
twenty-four hours, the error will probably not be more than 
two per cent, provided a proper method is used. 

If the condition of the fire is estimated at the beginning 
and end of the test, the fire should be cleaned and freed from 
ashes and clinker shortly before the test begins, and should 
then be spread in rather a thin even layer of clean glowing 
coal. Its height above the grate should be estimated with 
reference to some mark in the furnace that can be recognized 
readily. Just as long before the end of the test the fire 
should be cleaned and levelled in the same manner, and the 
thickness should be estimated with reference to the mark 
chosen at the beginning. The fireman is sure to have a clean 
bright fire at the beginning of the test, but he is apt to have 
a fire with much the same appearance that is half clinker at 
the end. The error from estimation may be very serious in 
such case, even though the test is 24 hours long. 

If the test is started and stopped with the grate empty, 
the boiler must be brought into good working condition about 
an hour before the test is to start, with all the brickwork 
thoroughly heated. The fire is allowed to burn low, and the 
steam-pressure is maintained by reducing the draught of 
steam from the boiler. Twenty or thirty minutes before the 
test starts, the fire is drawn or dumped and the grate and asii- 
pit are cleaned out. A new fire is started with wood, and 
coai is thrown on as soon as the wood is well alight. The 
time when coal is thrown on is counted as the beginning of 
the test. If the steam-pressure falls while the fire is drawn, 



306 S TEA M-B OILERS. 

the stop-valve may be nearly or quite closed to keep it from 
falling much below the working-pressure. Toward the end of 
the test the fire is allowed to burn low, and at the end of the 
test it is drawn out on the boiler-room floor and quenched with 
as little water as may be, not enough to leave it wet. The 
unburned coal is picked out by hand and weighed back, the 
clinker and ashes are separated and weighed together with the 
clinker withdrawn during the test and the ashes in the ash-pit. 

If any appreciable amount of coal falls through the grate, 
a sample from the ash-pit may be picked over by hand to es- 
timate the proportions of unburned coal in the ash. The coal 
in the ash is allowed for in calculating the per cent of ash in 
the coal, but is not added to the coal weighed back, for there 
is no way of burning coal thus lost through the grate. When 
a test is started with a wood fire, more or less coal is apt to 
fall through the grate in starting. This is drawn from the pit 
and fired over again. 

It is customary to allow the fire to burn low before draw- 
ing the fire at the end.of the boiler-test, both because it brings 
the fire more nearly to the condition at the beginning, and 
because it is a hard and unpleasant job to draw a thick fire. 
But the fire should be maintained at its normal condition 
until the end of the test approaches, and should be a good 
fire when drawn. Extraordinary results may be obtained by 
allowing the fire to burn nearly out at the end of the test, a 
very considerable amount of steam being formed by heat 
given out by the boiler-setting. It is unnecessary to say that 
such results are entirely misleading. 

The wood used for starting the fire is weighed and allowed 
for on the assumption that a pound of wood is equivalent to 
0.4 of a pound of coal. The total weight of wood used is not 
large. 

Temperature of Feed-water. — The temperature of the 
feed-water is taken by a thermometer in a cup filled with oil, 
screwed into the feed-pipe close to the check-valve. If the 



BOILER- TES TING. Z°7 

temperature varies, it may be read every five minutes: if it 
is found to be steady, less frequent intervals will do. 

Pressure of Steam. — The steam-pressure must be very 
nearly the same at the beginning and end of a test, and 
should remain nearly constant throughout the test. Read- 
ings are commonly taken every fifteen minutes, but the fire- 
man should be required to keep the pressure nearly constant 
at all times. 

The steam-pressure is taken by a spring-gauge like that 
shown by Fig. 92 on page 252. The gauge should be 
compared with a mercury column or a standard gauge both 
before and after the test, and a correction should be applied 
if necessary. If the pipe carrying pressure to the gauge fills 
up with water, allowance for the pressure of that column of 
water must be made. Each foot of water will give a pressure 
of about 0.43 of a pound per square inch. 

The reading of the barometer should be taken two or 
three times during a test. The reading in inches of mercury 
can be reduced to pounds per square inch by multiplying by 
the weight of a cubic inch of mercury, which is about 0.491 
of a pound. 

Very commonly the pressure of the steam is obtained 
indirectly by aid of a thermometer set in the steam- pipe. 
The absolute pressure corresponding to the temperature is 
then obtained from a table of the properties of saturated 
steam. The thermometer is readily standardized, and is not 
so likely to become unreliable as a steam-gauge. 

Most vertical boilers and some water-tube boilers give 
superheated steam ; in such case there shouid be both a 
thermometer and a gauge on the steam-pipe, to indicate tem- 
perature and pressure. The excess of the temperature by 
the thermometer above that corresponding to the absolute 
pressure of the steam, as found in a table of properties of 
steam, is the degree of superheating. 

Specific Heat of Superheated Steam. — The mean value 



°8 s TEA M-B OILERS. 



given by Regnault for the specific heat of superheated steam 
is 0.4808, or approximately 0.48. This property of steam 
can be used in calculating the amount of heat in steam due 
to superheating. 

For example, let the pressure by the gauge be 65.3 
pounds, and let the temperature be 350 F. by the thermom- 
eter. The absolute pressure corresponding to 65.3 pounds 
is 80 pounds, at which saturated steam has the temperature 
of 31 1°. 8 F. The superheating is consequently 

350 F. - 31 1°. 8 F. = 38°.2 F. 

The heat due to the superheating is 

0.48 X 38.2 = 18.3 B. T. U. 

When the steam is superheated, the formula for equiv- 
alent evaporation is changed from the form given on page 
135 to 

Wl o.48(*,-Q + *-+?-?■ 

1)0 — — , 

965.8 

in which t s represents the actual temperature of the super- 
heated steam, and t is the temperature corresponding to the 
absolute pressure of the steam determined from the reading 
of the gauge. 

Priming. — A boiler which has sufficient steam-space and 
free water- area will deliver steam which contains less than 
two per cent of moisture. 

Professor Denton* has pointed out that a jet of steam 
blowing into the air from a petcock will give a characteristic 
blue color if there is less than two per cent of water in the 
steam. If there is more than two per cent of moisture, the 
jet will be white. Since steam seldom contains less than 
one per cent of moisture under the usual conditions of 
ordinary practice, it is possible by this method to estimate 
the condition of steam with a probable error of one per cent. 
* Trans. Am. Soc. Mech. Engs., vol. x. p. 349. 



BOILER- TES TING. 



309 



The most ready way of determining the condition of 
steam is by the aid of a throttling-calorimeter, devised by 
Professor Peabody,* which depends on the fact that the total 
heat of steam increases with the pressure, so that dry steam be- 
comes superheated when the pressure is reduced by throttling. 
If the steam is only slightly primed, superheating will still 
take place, and the amount of priming can be determined 
from the temperature and pressure of the steam after it is 
throttled. If there is much moisture in the steam, it fails to 
superheat. 

A good form of this apparatus is shown by Fig. 136, 
consisting of a reservoir A to which the 
steam to be tested^is admitted through 
a half-inch pipe b with a throttling-valve 
near the reservoir. The steam flows 
away through an inch pipe d. At f is 
a gauge for measuring the pressure, and 
at c there is a deep cup for a ther- 
mometer to measure the temperature. 
The boiler-pressure may be taken from 
a gauge on the main steam-pipe near 
the calorimeter. It should not be taken 
from a pipe in which there is a rapid 
flow of steam as in the pipe b, since 
the velocity of the steam will affect 
the gauge-reading, making it less than 
tne real pressure. The reservoir is 
wrapped with hair-ielt ana lagged with wood to reduce radia- 
tion of heat 

When a test is made the valve on the pipe d is opened 
wide (this valve is frequently omitted), and the valve at b is 
opened wide enough to give a pressure of five to fifteen 
pounds in the reservoir. Readings are then taken of the 




Fig. 



130. 



Trans. Am. Soc. Mech. Engs., vol. x. p. 327. 



310 S TEA M-BOILERS. 

boiler-gauge, of the gauge at/, and of the thermometer at e. 
It is well to wait about ten minutes after the instrument is 
started before taking readings, so that it may be well heated. 

The method of calculation can be readily understood 
from the following 

Example. — The following are the data of a test made 
with a throttling calorimeter: 

Pressure of the atmosphere 14.8 pounds. 

Pressure by the boiler-gauge ,.. 69.8 " 

Pressure by the calorimeter-gauge.... 12.0 " 

Temperature in the calorimeter 268°.2 F. 

The absolute pressure in the boiler was 

69.8 + 14-8 = 84.6 pounds, 

at which the heat of vaporization is 892.7 B. T. U. and the 
heat of the liquid is 285.3 B. T. U. So that with x part of 
a pound steam (and 1 — x priming) the heat in one pound of 
moist steam was 

892.8^+285.3, 

in which x was to be determined. The absolute pressure in 
the calorimeter was 

12 -f- 14.8 = 26.8 pounds, 

at which the temperature was 243°.9 F>, and the total heat 
was 1 1 56.4 B. T. U. The heat due to superheating was 

0.48(268°. 2 - 243°. 9 ) = 11. 7 B. T. U., 

and the heat in one pound of steam in the calorimeter was 

1 156.4+ 1 1.7 = 1 168. 1 B.T.U. 

But the process of throttling neither adds nor subtracts 
heat, consequently 

892.8^+ 285.3 = 1168.1, 
or x = o.< 



BOILER- TES TING. 3 I l 

and the priming was 

100(1 — 0.988) == I, 2 per cent. 

The calculation can be conveniently expressed by an equa- 
tion in which r and q are the heat of vaporization at the abso- 
lute boiler-pressure, and Aj and t x are the total heat and the 
temperature at the absolute pressure in the calorimeter, all 
taken from a table of proportions of steam; while t s is the 
temperature of the superheated steam in the calorimeter. 
Then 

xr+#= A, + 0.48(4-/,,; 

x = ,i, + 0.48(4-0 -g 
r 

It has been found by experiment that no allowance need 
be made for radiation from the calorimeter if made as de- 
scribed, provided that 200 pounds of steam are run through 
it per hour. Now this quantity will flow through an orifice 
one fourth of an inch in diameter under the pressure of 70 
pounds by the gauge, so that if the throttle-valve be replaced 
by such an orifice the question of radiation need not be con- 
sidered. In such case a stop-valve will be placed on the pipe 
to shut off the calorimeter when not in use; it is opened wide 
when a test is made. If an orifice is not provided, the 
throttle-valve may be opened at first a very small amount 
and the temperature in the calorimeter noted after a few min- 
utes; the valve may be opened a trifle more, whereupon the 
temperature will usually rise, showing too little steam used. 
If the valve is opened little by little till the temperature stops 
rising, it will then be certain that enough steam is used to 
reduce the error from radiation to a very small amount. 

Various modifications of the throttling-calorimeter have 
been proposed, mainly with a view of reducing its size and 
weight. Almost any of them will prove satisfactory in prac- 
tice, but some will be found to be liable to error from radia- 



312 



S TEA M-BOILERS. 



tion or from the fact that there is not sufficient opportunity 
for the steam to come to rest and properly develop the super- 
heating due to throttling. One great advantage of this 
instrument is that ordinary care with ordinary gauges and 
thermometers gives sufficient accuracy. For example, with 
ioo pounds absolute boiler-pressure and with atmospheric 

pressure in the calorimeter, an error 
of half a degree by the thermometer, 
or half a pound by the boiler-gauge, 
or a third of a pound by the calo- 
rimeter-gauge will each give an error 
of one-tenth of a per cent in the 
priming. 

If steam contains more than three 
per cent of priming, the amount of 
moisturecan be determined by a gooa 
separator, which will remove nearly 
all the moisture. It remains then 
to measure the steam and water sep- 
arately. The water may be best 
measured in a calibrated vessel or 
receiver, while the steam may be 
condensed and weighed, or may be 
gauged by allowing it to flow through 
an orifice of known size. A form 
of this instrument devised by Professor Carpenter* is shown 
by Fig. 137. 

Steam enters a space at the top which has sides of wire 
gauze and a convex cup at the bottom. The water is 
thrown against the cup and finds its way through the gauze 
into an inside chamber or receiver, and rises in a water-glass 
outside. The receiver is calibrated by trial so that the 
amount of water may be read directly from a graduated scale. 




Fig. 137. 



* Trans. Am. Soc. Mech. Eng?,, vol, xvit. p. 608. 



BOILER- TES TING. 3 I 3 

The steam meanwhile passes into the outer chamber which 
surrounds the inner receiver, and escapes from an orifice at 
the bottom. The amount of steam may either be calculated, 
by a method to be explained, from the diameter of the orifice 
and the pressure of the steam, or it may be condensed and 
weighed or measured. The latter is the more accurate way, 
and it has the advantage that then there is no error from 
radiation, for the inner receptacle is well protected by the 
outer chamber, and condensation in the outer chamber is 
collected and weighed with the steam. If the instrument is 
well wrapped and lagged, and if a sufficient quantity of steam 
is used, then the error from radiation can be neglected, just 
as was found to be. the case with the throttlincr-calorimeter. 
This instrument, for want of a better name, is called a separator 
calorimeter; it is a question whether either it or the throttling- 
calorimeter are properly calorimeters at all, and whether it 
would not be better to call both priming-gauges. 

It is customary to take a sample of steam for the calori- 
meter or priming-gauge through a small pipe leading from 
the main steam-pipe. The best method of securing a sample 
is an open question ; indeed it is a question whether we ever 
get a fair sample. There is no question but that the com- 
position of the sample is correctly shown by either of the 
priming-gauges described. It is probable that the best way 
is to take steam through a pipe which reaches at least half- 
way across the main steam-pipe, and which is closed at the 
end and drilled full of small holes. It is better to have the 
samping-pipe enter the steam-pipe at the side or at the top of 
the main, so that any water that may trickle along the bottom 
of the main shall not enter the calorimeter. Again, it is better 
to take a sample from a pipe through which steam flows 
upward. The sampling-pipe should be short and well wrapped 
to avoid radiation. 

If the steam from the boiler can be wasted during the test, 
then the entire steam delivered by the boiler may be passed 



3 1 4 S TEA M- BOILERS. 

through a large priming-gauge, and the difficulty of getting a 
sample may be avoided. 

Flow of Steam.— It has been shown by Rankine * that 
the flow of steam through an orifice into the atmosphere may 
be represented by an empirical equation, 

70 

in which Wis the number of pounds of steam per second, A 
is the area of the orifice in square inches, and p is the absolute 
pressure of the steam. This equation, which has already 
been mentioned in connection with safety-valves, can be 
applied only when the absolute steam-pressure is more than 
double the pressure of the atmosphere; that is, the pressure 
of the steam must be 15 pounds by the gauge, or more. 
Experiments made in the laboratory of the Massachusetts 
Institute of Technology f show that this equation is liable to 
an error of about two per cent, but this error may be deter- 
mined by direct experiment for a given orifice under various 
pressures, and then a correction can be applied which will 
reduce the error to a fraction of one per cent. 

It appears then that the use of an orifice to determine the 
amount of steam in Professor Carpenter's separator priming- 
gauge is at least questionable unless direct experiments are 
made to determine the correction to be applied. On the 
other hand, the amount of steam used by a throttling prim- 
ing-gauge may be very properly determined by allowing it 
to flow through an orifice, since the total amount of steam 
used by the calorimeter is small. 

The same equation may be used for calculating flow of 
steam from one reservoir to another provided that the pres- 
sure in the second reservoir is less than half that in the first 



* The Engineer, vol. XXVII. p. 359, 1869. 
f Trans. Soc. Am. Engs., vol. xi. p. 187. 



BOILER- TES TING. 3 I $ 

reservoir. This allows us to gauge small quantities of steam 
used for any purpose, at a pressure that is less than half the 
boiler-pressure; for example, for running a steam-pump. A 
convenient arrangement for gauging the flow of steam in an 
inch pipe consists of a reservoir three feet long, made up of 
three-inch piping, and fittings divided at the middle by a 
brass plate through which there is an orifice of proper size. 
If the pipe carries steam at ioo pounds absolute, at a velocity 
of ioo feet a second it will deliver 

7id* 3-i4i6 X ( T V) 2 

X 100 = — X 100 = 0.5455 

4 4 

cubic feet per second. The density or weight of one cubic 
foot of steam at 100 pounds absolute is 0.2271 pounds. So 
that the pipe will carry 

0.5455 X 0.2271 = 0.124 

of a pound of steam per second. If this weight is put for W 
in Rankine's equation, and if A is replaced by \ nd 2 , we 
shall have 

7td 2 X 100 
o. 124 = 



4 X 70 



or 



, /OI24. 

V 3-Hi 



X 4 X 70 _ l 



6 X 100 3 

of an inch, nearly, for the diameter of the orifice for gauging 
the flow of steam. With an orifice of approximately the 
right size, the flow of steam may be regulated by a valve 
below the gauging device; for example, by the throttle-valve 
of the pump. 

Flue-gases. — At frequent intervals samples of flue-gases 
should be taken from various places, such as back of the 
bridge, from the uptake, and from the chimney. These sam- 



3i6 



S TEA M-B OILERS. 



pies are analyzed as soon as may be by Orsat's apparatus, as 
described on page 56. 

Though not commonly done, it would be well if a con- 
tinuous sample could be taken in a reservoir from which 
samples for analysis could be taken at intervals. 

Draught-gauge. — The draught given by a chimney is 
seldom more than an inch or an inch and a half of water. It 
can be measured roughly by a simple U tube filled with water. 
An instrument for accurate determinations of draught should 
be at once simple and certain in its action. 

The draught-gauge shown by Fig. 138, devised by Prof. 




Fig. 138. 



Miller, has been used with satisfaction for this purpose. It 
consists of two pieces of three-inch brass pipe connected by a 
half-inch pipe at the bottom. One of the pipes is closed at 
he top and can be connected to the chimney by a small pipe 
with a valve as shown. The other piece of brass pipe is open 
and has a hook-gauge, reading to 1/1000 of an inch, suspended 
in it. In preparing for a reading, the closed tube or leg is 



B OIL ER- TES 7 VNG . 3 ' 7 

shut off from the chimney and opened to the atmosphere ; the 
water then stands at the same height aa, a'a, in both legs. 
The closed leg is now shut off from the air and connection is 
made with the chimney, whereupon the level falls to bb in the. 
open leg and rises to b'b' in the closed leg. As the two legs 
have exactly the same internal diameter, the fall ab is half the 
draught, measured in inches of water. The hook-gauge is set 
to the level aa when the closed leg is open to the air, and to 
the level bb when it is connected to the chimney. The 
difference of the readings multiplied by 2 is the draught in 
inches of water. The reading by the hook-gauge can readily 
give an acuracy of i/iooo of an inch, which is sufficient for 
this purpose. 

Pyrometers. — The determination of high temperatures, 
as in flues and chimneys, is difficult and uncertain. Most 
commercial pyrometers, depending on the unequal expansion 
of metals, are unreliable if not misleading; not only is the 
scale of such a pyrometer likely to be incorrect, but the zero 
of the scale is liable to change during use. 

The Chatelier pyrometer has been used with satisfaction 
at the Massachusetts Institute of Technology for measuring 
temperatures in flues and chimneys. It consists essentially 
of a thermoelectric couple made by joining the ends of two 
wires, one of platinum and the other of platinum alloyed with 
ten per cent of rodium. All but about four inches of the wire 
at the junction is incased in fire-clay inside an iron pipe 
about four feet long. From the wires of the pyrometer con- 
nection is made to a sensitive galvanometer in a separate 
observing-room. The deflection of the galvanometer is indi- 
cated by a ray of light reflected from a mirror on the needle 
and moving over a graduated scale. The scale is set to read 
zero when the junction of the wires is at the temperature of 
the atmosphere. The junction is then immersed successively 
in baths of substances which melt at various high tempera- 
tures, such as sulphur and naphthaline. The readings of the 



3 1 8 S TEA M-B OILERS. 

ray of light when the juncture is in such baths fix known 
points on the arbitrary scale from which intermediate tem- 
peratures may be estimated directly. It is convenient to use 
a curve for this purpose with scale-readings for abscissae and 
with corresponding temperatures for ordinates. After the 
scale is deterimned the pyrometer may be introduced into the 
place or places where temperatures are to be measured, and 
readings are taken from which the temperatures are deter- 
mined by interpolation on the curve just described. 

Air-supply. — The air for a furnace may be made to enter 
through a temporary mouthpiece fitted to the ash-pit doors. 
This mouthpiece irnay be of galvanized iron, circular in sec- 
tion and about three feet long. Its cross-section should have 
an area equal to that of the door or doors leading to the ash- 
pit. The velocity of the air passing through the mouthpiece 
can be measured by an anemometer. The area of the mouth- 
piece multiplied by the velocity in feet per second gives the 
volume of air supplied to the ash-pit in cubic feet per second. 
From this may be calculated the volume and weight of air 
supplied to the ash-pit per hour or for the entire test; which 
weight divided by the total coal consumption gives the air 
per pound of coal burned. 

It should be noted that the anemometer is liable to an 
error of from two to five per cent, and further that air enter- 
ing through the fire-doors and elsewhere than through the ash- 
pit is not measured. 

Sample Test. — The test given on page 319, made at the 
Massachusetts Institute of Technology, may serve as an 
example of a convenient arrangement for reporting the data 
and results of a boiler-test. 

The average pressure of the air and of the steam in the 
boiler are liable to vary slightly during the test; the average 
pressures were obtained from readings taken at regular inter- 
vals during the test. The same may be said of the tempera- 
ture of the feed-water. 



BOILER-TESTIXG. 



319 



BOILER-TEST. 

j) ATE Dec. 28, ""or—Jan. 2, 'Q2. 

Duration of Test £^ hours. 

Average pressure of air £fr Sl lbs. per sq. in. 

" gauge-pressure /00 -Q " 

" temperature of feed-water I32 - 02 F. 

Kind of coal used L ackawanna . 

Per cent of moisture in coa 



1. Description of Boilers: Babcock cV Wilcox, No, 
10S tubes 4" dia., if 8" lont; ; outside area 


1. 

, 1 907 3 


12 


" 4" dia. 


' 


6' " 


S6.S 


2 drums 3' dia., X H 


; one-half 0/ shell, 


100.2 



Boiler No. J_\ Boiler No. 



, JNo.^,J^in. by^in.^ 
Gratc-surfaceX >• Area, feet 

(No.__, in. by in 

Water-heating surface, feet 

Ratio of water-heating surface to grate-surface 

Lbs. coal fired, including coal equivalent of wood 

Unburned fuel 

Coal burned, including coal equivalent of wood 

Average coal burned for '5 minutes 

Total refuse from coal 

Total combustible 

Average combustible for J 5 minutes 

Average lbs. of air for 7 ->" minutes 

Air per lb. of coal 

Air per lb. of combustible 

Quality of steam, saturated steam taken as unity 

Total water pumped into boiler and apparently evaporated.. 

Water apparently evaporated per lb. of coal burned 

Water actually evaporated, corrected for quality of steam 

Equivalent water evaporated into dry steam from and at 
212° F 

Equivalent water evaporated into dry steam, from and at 
212° F., per lb. of coal burned 

Equivalent water evaporated into dry steam, from and at 
212° F., per pound of combustible 

Coal burned per sq. foot of grate surface per hour 

Water evaporated, from and at 212 F., per sq. foot of heat- 
ing-surface per hour ... 

* Fires not drawn. 



43-it> 



64.6JQ 



64,630 



126.2 



S660 



55-Q70 



i5j3S 

o Q83 



5 4*. 70+ 



8.40 



530,463 



6/4.300 



0.8 



320 STEAM-BOILERS. 

The description of the boiler under item I is brief and yet 
sufficient to identify it, and gives the data for calculating 
heating-surface. The grate-surface, heating-surface, and their 
ratio are calculated from the dimensions of the boiler and 
furnace, and given in the 2d, 3d, and 4th items. The 5th 
item gives the total weight of coal fired; as the fires were not 
drawn, no wood was used and no coal was withdrawn at the 
end of the test. Consequently the 7th item, coal burned, is 
the same as the 5th. 

The 9th item gives the weight of all the clinker and ashes 
produced during the test. The coal burned, minus the 
refuse, gives the total combustible for the test, set down at 
item 10. 

The air-supply is calculated at intervals of 15 minutes 
during the test, from the anemometer readings and the condi- 
tion of the atmosphere as it enters the galvanized-iron tem- 
porary mouthpiece of the furnace. This is likely to vary 
considerably, being greatest immediately after fresh coal is 
fired. Item 12 gives the average from the several calculations 
during the test. The coal and combustible for 15 minutes 
given by items 8 and 1 1 are calculated for comparison with 
the air for the same time. Thus the air per pound of coal is 
calculated by dividing item 12 by item 8; and in like manner 
the 14th item is calculated from the nth and 12th. 

The quality of the steam was obtained from time to time 
during the test by a throttling-calorimeter, like the one for 
which a description and calculation are given on page 309. 
The average from the several determinations is given by item 
15. The priming was 

100(1.000 — 0.983) = 1.7 per cent. 

The equivalent evaporation for the total coal (given by 
item 18) was calculated, by a method like that given on page 
133, from the temperature of the feed-water, the pressure in 



BOILER- TES TING. 3 2 1 

the boiler, and the quality of the steam; using the total water 
apparently evaporated given by item 16. 
The absolute boiler-pressure was 

109.9+ M-85 = 124.8 pounds. 

The corresponding heat of vaporization and heat of the 
liquid are 871.8 and 3 1 5 . 1 ; the heat of the liquid at I22°.9 
(the temperature of the feed-water) is 91.0. Consequently 
the total equivalent evaporation from and at 212 F. was 

548,794(0.983X^8+ 3.5.. -90 = 6l4>300 pounds . 

The equivalent evaporation per pound of fuel (item 20) is 
obtained by dividing the quantity just found by the total 
coal burned (item 7). In like manner the equivalent evapora- 
tion per pound of combustible is obtained from item 10. 

The coal burned per square foot of grate-surface per hour 
is obtained by dividing the total coal burned by the area of 
the grate and by the duration of the test. Thus 

64,639 

= 9.8 pounds. 



51.3 X 128 



The equivalent evaporation per square toot of heating- 
surface per hour (item 23) is obtained by dividing the total 
equivalent evaporation (item 19) by the heating-surface and 
by the duration of the test. Thus 



6l 4.3QO 

- = 2.17 pounds. 



2214 X 

Remark. — In this chapter are given the observations that 
are required and the precautions to be taken in making an 
ordinary boiler-test. It is, however, intended rather as a 



322 STEAM-BOILERS. 

description for the student than as a guide for the engineer, 
who must learn how to make tests by experience. Many of 
the processes and observations are so simple that they may be 
intrusted to any careful and intelligent person; the conduct 
of the test must receive the attention of a competent engineer, 
for there is no expert work that an engineer may be called 
upon to do in which there is more chance for error and 
deception than in making a boiler-test. 



CHAPTER XI. 
BOILER DESIGN. 

In order to bring together the principles and methods 
which have been given in the preceding chapters, they will be 
applied to the design of a boiler. Designing of any sort is an 
art that is guided and controlled by practical considerations 
and theoretical principles, and which can be acquired by prac- 
tice only. The design of a boiler, like many other designs, 
is further modified to meet the requirements of government 
boards of inspection, or to conform to the inspection-rules of 
insurance companies. These rules and requirements vary 
from place to place and from time to time ; they must be 
known to the designer, but they have no place in a text-book. 
A simple and common type of boiler has been chosen for 
design ; the methods, with proper modification, can be applied 
to other types, and the general principles illustrated are much 
the same for all types. 

Type of Boiler. — The kind of boiler used in a given 
locality depends on custom, on the kind of water used, and on 
the cost and quality of fuel. Deviation from common prac- 
tice should be made only for sufficient reason. Where water 
is bad or where fuel is cheap, the plain cylindrical boiler or a 
flue-boiler will be chosen. With clean, soft water the cylin- 
drical tubular boiler, like that shown by Plate I, has been 
found to be convenient, economical, and cheap. All these 
boilers have external furnaces, so that the shell is in part 
exposed to the fire. Now plates exposed directly to the fire 
should not be more than half an inch thick ; 3/8 of an inch is 
preferable. Though thicker plates are sometimes used, this 

323 



324 S TEA M-B OILERS. 

consideration limits the size of boilers of this type when high 
pressures are used. The importance of high efficiency for the 
longitudinal riveted joint becomes apparent in this connec- 
tion. 

Internally-fired boilers, like the Lancashire or the Scotch 
marine boiler, are not limited in diameter by this reason. 
The marine boiler sometimes has plates an inch and a quarter 
thick ; the fact that so great a thickness is undesirable some- 
times serves as a check on the size of such boilers. 

General Proportions. — Whatever may be the type of 
boiler chosen, there must be provided — 

1. Sufficient grate-area to burn the fuel required under the 
available draught. 

2. Suitable combustion-space to properly burn the fuel. 

3. Sufficient area of flues or tubes to carry off the products 
of combustion. 

4. Sufficient heating-surface to absorb the heat generated. 

5. Proper water-space to prevent too great a fluctuation 
of the water-level when there is an irregular demand for steam. 

6. Suitable steam-space to prevent too great a fluctuation 
of pressure when steam is taken at intervals, as for the cyl- 
inder of a steam-engine. 

7. Sufficient free-water area for disengagement of steam. 

The last three conditions are not fulfilled by most water- 
tube boilers; some such boilers depend on a separator for 
disengaging steam from water. 

Problem for Design. — Let it be required to determine 
the main dimensions and some of the details of a hori- 
zontal cylindrical tubular boiler to develop 80-horse power 
A. S. M. E. standard (page 135). Let the working-pressure 
be 150 pounds per square inch by the gauge, and the test- 
pressure 225 pounds, or once and a half the working-pressure. 

Assume that anthracite coal will be used, and that it will 
give an equivalent evaporation of 9 pounds of water per 
pound of coal from and at 212 F. Assume further that 12 



BOILER DESIGN. 325 

pounds of coal will be burned per square foot of grate-surface 
per hour. 

The heating-surface may be about thirty-seven times the 
grate-surface. Tubes 16 feet long will be used, which length 
should not much exceed sixty times the diameter. 

The area through the tubes will be made about 1/7.5 °f 
the grate-area. 

Grate - area. — The A. S. M. E. standard requires that 
34.5 pounds of water per hour shall be evaporated from and 
at 212 F. for each horse - power. The total equivalent 
evaporation will consequently be 

80 X 34.5 = 2760 pounds per hour. 

With an equivalent evaporation of 9 pounds of water per 
pound of coal the coal burned will be 

2760 -T- 9 = 307 pounds per hour. 

With a rate of combustion of 12 pounds of coal per square 
foot of grate surface per hour, the grate-area must be 

307 -5- 12 =25.6 square feet. 

Tubes. — A common rule for finding the diameter of 
tubes is to allow one inch for each four feet of length when 
soft coal is used, and five feet when hard coal is used. A 
tube three inches in diameter will very nearly fulfil this 
condition. 

The table of proportions of flue-tubes in the Appendix, 
gives the area of the internal transverse section of such a tube 
as 6.08 square inches; the external area is 7.07 square inches. 
The internal circumference is 8.74 inches, and the external 
circumference is 9.42 inches. 



326 S TEA M-B OILERS. 

The aiea through the tubes has been chosen as 1/7.5 °f 
the grate-area, equal to 

25.6 X 144 . , 

= 402 square inches. 

7-5 

Since the area through one tube is 6.08 square inches, 
there will be required 

492 -=-6.08 = 80.8, 

or, more properly, 81 tubes. It may be found convenient in 
laying out the tube-sheet to use more than this number of 
tubes; a less number is of course improper. 

Steam-space. — A good rule for this type of boiler is ta 
allow from 0.8 to 1 cubic foot of steam-space per horse- 
power, which gives from 64 to 80 cubic feet for this boiler. 
We will assume 80 cubic feet. 

For sake of comparison, calculations will be made also by 
rules given on page 132. Thus for certain boilers working at 
moderate pressures it is found that the steam-space may be 
made equal to the volume of steam used by the engine in 20 
seconds. Suppose that this boiler, though designed for 150 
pounds pressure, may run at 70 pounds pressure, and may 
supply an 80 horse-power engine which uses 30 pounds of 
steam per horse-power per hour. 

Now the volume of one pound of steam at 70 pounds by 
the gauge, or 85 pounds absolute, is 5.125 cubic feet. So 
that the engine will use 

80 X 30 X 5-125 = 12,300 

cubic feet of steam in an hour, or 

20 ra 

X 12300 = 68 



3600 



cubic feet in 20 seconds. This is about the lower limit by 
the rule used above. It is clear that the steam-space would 



BOILER DESIGN. $2 J 

be very small if determined by this rule for an engine using 
steam at 150 pounds pressure. 

Another rule makes the steam-space from 50 to 140 times 
the volume of the high-pressure cylinder of the engine; 50 
for very high pressure and high speed, 140 for slow speed 
and low pressure. For medium speeds and pressures 60 to 
90 may be used. 

The boiler under consideration may supply steam to a 
triple-expansion engine which has a high-pressure cylinder 9 
inches in diameter by 30 inches stroke, so that the volume is 
1. 105 cubic feet. According to this the steam-space needed 
is 66 to 99 cubic feet. 

Diameter of Boiler. — For this type of boiler the steam- 
space is commonly made one third and the water-space two 
thirds of the contents of the boiler. To the contents of the 
boiler there must be added the space occupied by the tubes to 
find the volume of the cylindrical shell. Now we have de- 
cided to use 81 tubes 3 inches in diameter and 16 feet long. 
The area of the external transverse section has been found to 
be 7.07 square inches. The space occupied by the tubes is 
consequently 

81 x 7.07 X 16 



44 



= 64 cubic feet. 



To this add steam-space, 80 

and water- space, 160 



Making in all, 304 " iC 

The cylinder is 16 feet long, so that its transverse area is 

304 -r- 16 = 19 square feet; 

which corresponds to a diameter of 59.02 inches, or nearly 60 
inches. This will be taken as the trial diameter; it may re- 
quire change in proportioning other parts of the boiler. 

The method of determining the main dimensions of a 



328 S TEA M-B OILERS. 

boiler from the steam-space will require modification if it is 
applied to any other type of boiler. Even when applied to 
a given type it leaves much to the judgment of the designer, 
who may find difficulty in using it unless he is accustomed to 
working on that particular type. If the designer has at hand 
the dimension of several boilers of a given type, he may pre- 
fer to select the main dimensions for a new design directly, 
with the reservation that such dimensions may be modified 
as the design proceeds. This is commonly done by the 
designers of marine and locomotive boilers. 

Heating-surface. — The heating-surface of a cylindrical 
tubular boiler consists of all the shell below the supports at 
the side wall, all the inside of the tubes, and part of the rear 
tube-plate. Usually half of the cylindrical part of the shell 
is heating-surface. In the case in hand the heating-surface, 
exclusive of the tube-plate, will amount to 

au u r w 3-H 16 X 60 X 16 

Shell - )< ^— = 125.7 sq. ft. 

^ T „ 8 -74 X 16 

Tubes.... 81 X —^ = 943.9 " " 



Total 1069.6 " " 

The grate-surface is to be 25.6 square feet, so that the 
ratio of grate-surface to heating-surface will be at least as good 



25.6 : 1069.6 :: 1 : 41^. 



The actual ratio will be more favorable as it will appear 
advisable to use more than 81 tubes, and the back tube-sheet 
remains to be allowed for. 

Water-level. — It is now necessary to determine the posi- 
tion of the water-level to see if there will be sufficient free- 
water surface and sufficient distance from the water-level to 
the shell above it. 



BOILER DESIGN S 2 9 

Since the whole boiler is cylindrical, the area of the head 
of the boiler exposed to steam and to water will have the 
same ratio as that of the steam-space to the water-space. 
Consequently the area of the head above the water-level must 
be one third of the total area of the head less the combined 
areas of the tubes. 

The area of a circle having a diameter of 60 inches is 
2827.4 square inches. The area of 81 tubes each having an 
external cross-section of 7.07 square inches will be 

81 x 7-07 = 572.7 

square inches. The area of the head exposed to steam is 
consequently 

2827.4- 572.7 = 

square inches. We need now to know the height of a seg- 
ment of a 60-inch circle, which has the area of 751.6 square 
inches. The second problem in the explanation of the use of 
a table of segments (see Appendix; gives for the tubular 
number corresponding to the area 

75K6 0.2088; 



60 X 60 



for which the ratio of the height to the diameter is 0.312. 
The height of the segment is therefore 

0.312 X 60 = 18.7 inches. 

This gives sufficient height above the water, and sufficient 
free-water surface. The water-level will be 

30 - 18.7 = 11. 3 

inches above the centre of the boiler. 

Factor of Safety. — It has been pointed out that the actual 
factor of safety of boiler-shells is usually four or five when the 
boiler is built. The apparent factor of safety for some parts 



330 STEAM-BOILERS. 

like stay-bolts may be greater, but such factors are illusory 
because the stays may be subjected to considerable irregular 
stress from unequal expansion. The apparent stress on stay- 
rods and bolts, from steam-pressure only, is frequently limited 
by inspection-ruies or by law. 

The factor of safety of a boiler which has been at work 
for some years is much affected by corrosion, which acts upon 
different parts of the boiler very differently, even when the 
corrosion is uniform. Thus a plate half an inch thick will 
have 7/8 of its original strength after it has lost 1/16 of an 
inch by corrosion. The weakest part of the plate, that is, 
the riveted joint, seldom suffers as much from corrosion as the 
whole plate at a distance from the joint, because the plate is. 
protected to some extent by the rivet-heads. Some forms of 
joint have an internal cover-plate, which protects the plate at 
the joint and the joint may be nearly as strong after corrosion 
as before. Very often old weak boilers fail by tearing the 
corroded plate outside the riveted joint. 

Stay-rods and bolts suffer much more from corrosion than 
plates. Thus a rod one inch in diameter has an area of 
0.7854 of a square inch. After corrosion to the extent of 
1/16 of an inch has taken place the diameter is 7/8 of an 
inch and the area is 0.6013, which is 

0.6013 -*- 0-7854 = 0.766 

ot the original area. Compare this with the plate which 
retains 7/8 or 0.875 of its thickness after the same amount of 
corrosion. Of course a smaller stay will suffer more, and a 
larger one less, in proportion. 

After the sizes of the parts of a boiler are decided upon it 
is well to make calculation to see that a factor of safety of 
four will remain after a reasonable amount of corrosion. Or, 
as in the case of stay-rods, the size may be calculated with a 
proper factor, and then the diameter may be increased to> 
allow for corrosion. 



BOILER DESIGN 33 1 

Thickness of Shell. — The final decision of the proper 
thickness of the shell for the boiler under consideration can- 
not be made until the efficiency of the joint is known; but 
the efficiency of any of the complex joints now in vogue can 
be found only when the thickness of the plate is known. It 
is therefore convenient to assume a factor of safety of about 
six and make a preliminary calculation. 

Thus for the boiler in hand we will get for the thickness 
(page 183) 

,_ I50X30 =049 



55,000 h- 6 
of an inch. A similar calculation with a factor of five gives 

t — = 0.q.L 

55,000^ 5 

of an inch. The shell will be either 7/16 or 1/2 an inch 
thick. Seven sixteenths will give an apparent factor of 
safety of 

55 ,000 X 7/16 = - 
150 X 30 D ' 35 ' 

After the allowance for the efficiency of the joint has been 
made this factor will be found to be about 4f . 

Longitudinal Joint. — The shell-plate is made as thin as 
possible because it will be exposed to the fire. Consequently 
the efficiency of the longitudinal riveted joint must be high if 
the real factor of safety is to be satisfactory. The strength 
of triple-riveted joints like that shown on page 201 ranges 
from 85 to 90 per cent. The joint with two cover-plates 
shown by Fig. 139, will be chosen. Following the method 
given on page 201, it appears that this joint may fail in one 
of five ways, for which the resistances are as follows: 

A. Tearing at outer row of rivets : 

Resistance = (P •— d)tft. 



332 



S TEA M-B OILERS. 



B. Shearing four rivets in double shear and one in single 

shear : 

and 2 

Resistance = f s . 

4 

C. Tearing at the middle row of rivets and shearing one rivet: 

nd* 
Resistance = (P — 2d)tf t -\ /,. 




Fig. 139. 

D. Crushing four rivets and shearing one : 

Resistance = ^dtf c ~\ / s . 

E. Crushing five rivets: 

Resistance = ^dtf c + dt c f c . 

The diameter of rivet will be found by equating the 
resistances A and C. 

.-.(/>- d)tf t = {P- 2d)tf t + ^f s . 

# 4tf t 4X tVX 55>QQQ „ AQ 

. . a = — 7- = ■ = 0.05. 

n fs 7195 1° 00 



BOILER DESIGN. 333 

The rivet which was used was 13/16 of an inch when driven. 

There are several methods in which we may find the way 
in which the joint will fail, and then find therefrom the effi- 
ciency. One is that shown on page 202 by assuming a pitch 
and calculating the resistance of the joint to failure in each 
of the five several ways. Another method is to equate the 
five several resistances two and two and calculate the pitch ; 
the least pitch thus found must not be exceeded. Thus 

Equating B and C, 

4 4 

¥ f. 



X3.H.6x(^ 



45,000 \x 



7 55,000 ■ 16 

4x f 6 



Equating A and B, 



{P -d)tf t =^/,. 



9^ 



9 X 3.1416 



_i6/ 4SJ000. 13 

„ v 7 55,000^16 

4X T6 



Equating A and D, 



4 



3 3 V S TEA M-B OILERS. 

ft - 4* ft 

3-1416 X PI)' 

~ 4X i6 X 55,ooo + 7 X 55.ooo+i6 7A ' 

4X T6 

Equating A and E, 

(P-d)tf t = 4dtf c + dt c f e . 

Jt l It 

a vi? v 95,OQO a- I3/l6 X 3/8 w 95>QQO | 13 _ 76 
i6 X 55,000"^ 7/16 x 55,000+16 /# ' 

Here t t9 the thickness of the cover-plate, is taken to be 3/8 
of an inch. 

The greatest allowable pitch at the outer row of rivets is 
evidently 7.4 inches. 

Instead of going to the labor of solving all four of the 
above equations, we may find by some other method how the 
joint is likely to fail, and make up an equation involving 
those resistances only. Thus a rivet in the outer row may 
fail by shearing or by crushing at the cover-plate, which is 
here made thinner than the shell-plate. Equating the re- 
sistances of the two methods, we have 

—■/. = *#.. 

4 
or for a cover-plate 3/8 of an inch thick 

^ = 4XJ X 95,000 =iQi 

7t 45,000 

A rivet 1.01 inch in diameter will consequently be just as 



BOILER DESIGN. 335 

likely to fail by crushing as by shearing. But the resistance 
to shearing increases as the square of the diameter, while the 
resistance to crushing increases as the diameter. It is there- 
fore evident that a rivet larger than i.oi of an inch will fail by 
crushing, while a smaller rivet will fail by shearing. 

A similar calculation at the inner row, when the rivet 
bears against a cover-plate both inside and outside, and will 
consequently crush against the shell-plate, gives 

Js = taf e ; 

4 

, 2 XtV 95,000 , 

d = l¥ x — = o.6. 

it 45,000 

Here a rivet larger than 0.6 will crush, and one smaller 
will shear. It is now evident that a 13/16 rivet will shear 
at the outer row and will crush at the inner row. That is, for 
this joint the failure will occur by the method D, but not by 
the methods B or E. Then equating the resistances A and D, 
and solving for P, we get for the pitch at the outer row 7.4 
inches as before. The corresponding pitch at the calking 
edge of the outer cover-plate is 3.7 inches; we will choose for 
that pitch 3f inches, making the pitch at the outer row 71 
inches. 

The efficiency of the joint is 

p _ J 7I J.3 

100 = 100 X — ^ = 88.8 per cent. 

P 7\ 

In the preceding article the apparent factor of safety 
based on the whole strength of the shell-plate is 5.35. Al- 
lowing for the efficiency of the longitudinal joint, the real 
factor of safety when the boiler is new is 

0.888 X 5-35 =475. 



336 S TEA M-B OILERS. 

With this style of joint the shell-plate is protected from 
corrosion by the inner cover-plate, and the joint will lose 
little if any efficiency from corrosion. If it be assumed that 
the plate loses 1/16 of an inch by corrosion during the life 
of the boiler, then the strength of the plate will be one 
seventh less after corrosion, and the corresponding factor of 
safety will be 

5.35 X f = 4.6, 

which may be considered to be sufficient. 

Ring-seam — The stress on a transverse section of a 
homogeneous hollow cylinder from internal fluid pressure is 
one half the stress on a longitudinal section. It will in gen- 
eral be found that a single- or a double-riveted ring-seam is 
sufficient for any cylindrical boiler-shell. Marine boilers 
commonly have double-riveted ring-seams; externally-fired 
horizontal boilers seldom have the shell more than half an 
inch thick, and for that thickness, or less, single-riveted ring- 
seams are used. 

It is found in practice that ring-seams of horizontal ex- 
ternally-fired boilers may have a pitch of about 2 T 3 ^ inches for 
all thicknesses of plate from 1/4 to 1/2 of an inch. The 
diameters of rivets for such seams may be made about the 
size given in the following table : 

Thickness of plate \ T \ f T \ \ 

Diameter of rivet | \\ f \ \ 

The ring-seam in question has a circumference of about 

3.1416 X 60 = 188.2 

inches, which will allow us to use 84 rivets with a pitch of 
about 2.24 inches. This joint will fail by shearing the rivets. 
The efficiency of the joint is consequently the ratio of the 
resistance of a single rivet to shearing, to the resistance of 



BOILER DESIGN. 33/ 

a strip of plate as wide as the pitch. Consequently the 
efficiency is 



4 f * _ i X 3-i4i6 X ( -j-iJV X 45, 000 
///« 2.24 X -iV X 55.000 



■433. 



which is more than half of the efficiency of the longitudinal 
seam, and will consequently be sufficient. 

Lap. — The lap, or distance from the centre of the rivet to 
the edge of the plate, is usually taken as 1.5 times the diam- 
eter of the rivet used, which makes the distance of the edge 
of the hole from the edge of the plate equal to the diamccer 
of the rivet. For the single-riveted ring-seam this makes th^ 
lap equal to 

!-5 X If = 1.22. 

It is customary to calculate the width of lap required on 
the assumption that the metal between the rivet and the edge 
of the plate may be treated as a beam of uniform depth, fixed 
at the ends and loaded uniformly by the force which would 
be required to shear or crush the rivet, taking, of course, the 
larger. The width of the' beam is the thickness of the plate, 
the depth is the distance from the edge of the hole to the 
edge of the plate, and the length is the diameter of the rivet. 

Rivets in single-riveted seams fail by shearing. The loau 
is consequently the shearing resistance 

The maximum bending moment for a beam of uniform 
section fixed at the ends and uniformly loaded is equal to 
the load multiplied by one eighth of the span. The moment 
of resistance is equal to 

fl, 



33^ STEAM-BOILERS. 

in which /is the cross-breaking strength (about 55,000), /is 
the moment of inertia of the section, and y is the distance of 
the most strained fibre from the neutral axis. Here we have 

T th 3 Ji 

I — — , y= -, 
12 2 

representing the distance from the edge of the hole to the 
edge of the plate by h. 

Equating the bending moment to the moment of re- 
sistance, 

4 6 






nd % f s 

67 x 7 



3 x 3-Hi6 x 13 3 w 45*ooo ^ _ 
X — 0^77 

r 7 £% 5 5,000 7/ 

16 X -VX16 
16 

for the case in hand. The lap is consequently 

0.77+- x i| = 1.18 

2 16 

inches for the ring-seam, which is somewhat less than that by 
the arbitrary rule that it should be once and a half the diam- 
eter. 

A similar calculation for the cover-plates with the same 
diameter of rivet, but with a plate 3/8 of an inch thick, gives 
for the lap 1.24 or 1^ of an inch, while the arbitrary rule gives 
1.03 of an inch. It is probable that the lap may be consider- 
ably smaller than is given by the calculation by the beam 
theory, but for lack of direct experimental knowledge on this 
question it is not wise to make the lap much less than the 
calculation gives; we will consequently use 1^ of an inch for 
the lap of the cover-plates. 



BOILER DESIGN 339 

The rivets of the inner rows pass through both cover-plates 
and are in double shear, and consequently fail by crushing 
as is shown on page 335. The load to be used tor calculating 
the lap is therefore the resistance to crushing in front of the 
rivet ; that is, we here have for the load tdf c . The equation 
of bending moment and moment of resistance gives 

1 t/f 

ldXtdfc = f - 

k = <uM = L3 / 3 X 95,oo o = 6 

V 4/ 16V 4 X 45,ooo 

The lap is consequently 

0.926 + ^ Xy 6 = 1.27, 

or a little more than ij. The lap used is if of an inch. 

Tube-sheet. — The next step in the design is to lay out 
the tube-sheet on the drawing-board. If possible, the tubes 
should be arranged in horizontal and vertical rows as shown 
on Plate I. The distance between the tubes should not be 
less than three fourths of one inch ; one inch is better. On 
Plate I the horizontal rows are spaced one inch apart, while 
the vertical rows are only three fourths of an inch apart ; wider 
spacing for horizontal rows is more favorable for the free cir- 
culation of water and the disengagement of steam. The cir- 
culation is improved by having a space in the middle as shown 
on Plate I 

If a very large number of tubes are required for a given 
boiler, they may be arranged in vertical rows and in rows at 
30 with the horizon, as on Plate II. This arrangement is 
commonly used for locomotive boilers, but is not favored for 
stationary boilers. 

The common range of fluctuation allowed for the water- 



34° STEAM-BOILERS. 

line with this type of boilers is six inches, three above and 
three below the mean water-level. The tops of the tubes are 
set about three inches below low water-level. 

The tubes should nowhere be nearer than three inches 
from the shell, and the bottom row should be from four to six 
inches from the bottom of the boiler. 

The hand-hole near the bottom of the head should be 
placed as low as possible; the flat surface for the gasket should 
be at least 3/4 of an inch wide. No tube should be nearer 
than an inch from its edge. 

The tube plate is usually from 1/16 to 18 of an inch 
thicker than the shell-plating. The internal radius of the 
flange should not be less than half an inch. For plates half 
an inch thick or less the outside radius is commonly made one 
inch. 

In applying these principles to the tube-sheet for a boiler 
6c inches in diameter, as shown on Plate I, it appears that 84 
tubes may be used, spaced four inches horizontally and 3J 
vertically and with a space at the middle for circulation, pro- 
vided that the top of the upper row of tubes is 6J inches 
above the centre-line of the boiler. This brings the water- 
level 

6J + 6= I2i 

inches above the middle of the boiler, instead of 11.3 as cak 
culated on page 329; that is, the water-level is raised 1.2 of 
an inch or 1/10 of a foot. At 12 inches above the middle, 
the boiler is about 4J feet wide; the layer of water added has 
consequently a volume of 

1/10 X 4-5 X 16 = 7.2 

cubic feet. The effect is to reduce the steam-space from 80 
cubic feet (see page 326) to 72.8 cubic feet. But the rule 
used gave from 64 to 80 cubic feet, so that 72.8 cubic feet is 
a fair allowance. If the tubes were spaced nearer together 
in the horizontal rows and the space for circulation were 



BOILER DESIGN. 34 J 

omitted, the required number of tubes could be easily pro- 
vided for without raising the water-level. If in any case a 
satisfactory arrangement of tubes cannot be made with the 
diameter assumed from preliminary calculations of steam- and 
water-space, or from some other method, then a larger 
diameter must be used. 

Area of Uptake. — The area of the uptake, like the total 
area through the tubes, is made from 1/7 to 1/8 of the grate 
area. On page 326 the area through the tubes was found to 
be 492 square inches. The uptake may be made 12 inches 
deep, measured from front to rear. It will then be 

492 4- 12 — \\ 

inches wide, measured transversely. The opening through 
the top of the projecting shell at the front end will be made 
12 inches deep, as shown on Plate I, and must be cut down 
till it is 41 inches wide. The projecting end of the shell is 
made long enough so that a space of about one inch is left 
between the uptake and the calking edge of the front tube- 
sheet. 

Length of Sections. — The length of the rings or sections 
of the cylindrical shell is limited by the reach of the riveting- 
machine and by the width of plate obtainable. The sec- 
tions are often made the same length, though there is no other 
reason for this than the convenience in ordering material. 

o 

The two rear sections on Plate I are each made 68 inches from 
centre to centre of riveted joints, or, allowing \\ of an inch 
for lap at each end, the plates when finished are Jo\ inches 
wide The front section is 

14+ 54f + i* = 69J 

inches wide. In this case the plates could all be ordered 
about 72 inches wide. 

The front course which comes over the fire is an outside 
course, so that the flames may not strike directly against the 



342 S TEA M-BOILEKS. 

edge of the plate at the ring-seam. The length of the grate- 
is commonly about one third of the length of the boiler, 
which brings the first ring-seam over the bridge, where the fire 
is the hottest. It is well to avoid this by making the front 
section shorter, and the other sections longer. 

Manholes, Hand-holes, and Nozzles. — These fittings 
should be strong enough and stiff enough to carry the stresses 
which come from the direct steam-pressure and from the ten- 
sion in the pieces to which they are fastened; for example, 
the manhole-ring must be able to take the place of the piece 
of plate cut away at the hole. 

All these fittings can now be bought in the form of steeL 
forgings, made by a hydraulic flanging or forging machine. 
Gun-iron and cast steel are, however, much used. 

The determination of stresses in a manhole-ring, even if 
approximate methods are used, is both difficult and uncertain, 
and will not be considered here. Forms and dimensions that 
have been usecl in good practice may be taken for a guide in 
designing. A rule used by boiler-makers for forged rings, 
which, like that shown on Plate I, lie close to the shell-plate, 
is to make the section of the ring, exclusive of the lip, equal 
at least to the section of the plate cut away. The aid given 
by the lip against which the cover bears is considered to 
offset eccentric loading, etc. The ring of a steam-nozzle may 
be treated in the same way, though it is more efficiently aided 
by the cylindrical portion. Gun-iron manhole-rings should 
be I i of an inch thick, and nozzles may be i^ of an inch thick. 

An approximate calculation of the stress in the manhole- 
cover may be made by treating it as a beam supported at the 
ends and loaded by the steam-pressure and by the pull of the 
bolt at the middle; this last must be assumed, as it cannot be 
known. The calculated stress will be in excess of the actual 
stress, since the plate is supported all around. The handhole- 
plate may be treated in a similar way. Handhole-covers are 
frequently drawn up by a taper key instead of a bolt and nut r 



BOILER DESIGN. 543 

because the nut is exposed to the fire, and often cannot be 
removed with a wrench, after it has been in place some time. 

The bearing-surfaces of tlv? manhole-cover and the lip 
against which it bears should be machined to make them 
true and smooth, though this is not always done. The hand- 
hole-cover may be finished, but it bears directly against the 
plate, which of course is not finished. In any case the joint 
is made tight by a gasket which may be 3/4 of an inch wide 
for the hand-hole and from that width to an inch for the man- 
hole. 

Staying. — As is pointed out on page 222, the calculation 
of stresses in a flat plate supported at intervals can be 
determined only by the application of the theory of elasticity; 
and the only determinate case is that in which the supported 
points are in equidistant rectangular rows, dividing the sur- 
face into squares. This case applies directly to the staying 
of the fire-box of a locomotive by stay-bolts. Whatever 
system of arranging the supported points is finally chosen, it 
is convenient to make a calculation for the determinate case, 
with the points in equidistant rows, in order to get a standard 
with which the chosen system may be compared. 

The equation for finding the stress in a flat plate supported 
at points in equidistant rectangular rows is 

2 tf 

in which a is the distance of points in a row, t is the thickness 
of the plate, and p is the steam-pressure in pounds per square 
inch. In the design in hand t — 9/16 of an inch and/ = 
150 pounds. Assuming 

/=tV X 55,ooo= 5500, 
and solving for a, we have 



/9/t* / 9X 550 X 9X 9 , • , 

a = V 2 J = V 2^Tic7x-Y6^ri6 = 7 + mches - 



344 S TEA M-B OILERS. 

If the distance between supported points is made less than 
7 inches, whatever the system of arrangement may be, we 
may be confident that the stresses will not exceed 5500 
pounds; in this case stresses in the plate are due only to the 
pressure on the plate, since the shell of the boiler is self-sup- 
porting. 

In the several ways of staying the flat ends of boilers 
shown on pages 150 to 154 the plate is riveted to channel- 
bars, angle-irons, or crowfeet, which in turn are supported by 
stay-rods. The rivets are in direct tension, and are subject to 
initial stresses due to the contraction when they cool; it is 
customary to limit the apparent working stress to 6000 
pounds. Rivets less than 3/4 of an inch are seldom used, 
since in practice they are found to be too much affected by 
initial stress due to cooling. Large rivets are also considered 
to be undesirable. We will choose here 13/16 for the rivets. 

If each rivet sustains the pressure on a square a inches 
wide, then the stress per square inch on the rivet will be 

— /* = 150 X a\ 

4 

in which d is the diameter and f s is the tensional stress. 
Assuming f s = 6000 and d— 13/16, and solving for a, we 
have 



a > = \l 



71 x 13 X 13 X 6000 

-^ — 4.55 inches. 

150 X 16 X 16 



This gives for the limiting distance of rivets 4.55 inches. 
Of course a less distance may be used if convenient. 

In some cases the pitch of the rivets may be controlled by 
the system of staying. For example, the rods used with 
crowfeet are seldom more than \\ of an inch in diameter, 
because larger rods may bring too large a local stress where 
they are riveted to the cylindrical shell. Rods one inch or 
an inch and an eighth are frequently used. A double crow- 



BOILER DESIGN, 345 

foot has four rivets, each of which will carry one fourth of the 
load on the stay-rod. A stay-rod i \ of an inch in diameter, 
and limited to a stress of 7500 pounds, may carry a pull in 
the direction of its length of 

7500 X (l}) a = 11,720 pounds. 

If the rod makes an angle of 20 with the shell-plate, the pull 
which it will exert perpendicular to the head will be 

1 1,720 cos 20 = 1 1,720 X 0.93969 = 1 1,013 

pounds, so that each rivet will carry about 2750 pounds. 
If each rivet supports a square having the side a 2 exposed to 
the pressure of steam at 150 pounds, then 

11,013 = 150 X a,\ 
or 



V iqo 



8 inches. 

5< 

Laying out Stays. — Having selected the form of staying 
to be used, the plan must be laid out on the drawing-board, 
giving proper attention to practical considerations, such as 
the way in which the stays are to be inserted, and taking care 
that accessibility is not too much interfered with. Fig. 140 
repeats the upper part of the head of the boiler shown by 
Plate I, with certain additional dotted lines, which will be 
referred to in the explanation of calculations. The area to 
be stayed is considered to be limited by the upper row of 
tubes, and by a dotted line drawn ij of an inch from the 
inside of the shelh This line is drawn at the right only; it is 
very nearly the place where the rounded corner of the flange 
joins the flat surface of the head. The distance of the lowest 
row of rivets from the top row of tubes, and of the outer row 
of rivets from the dotted line, may be as great as their maxi 
mum distance from each other. Rivets should not be placed 
nearer than 3 inches from the tubes, lest the expansion of the 



34-6 s TEA M-B OILERS. 

tubes should start leaks. Rivets may be placed near the 
dotted line, if that is convenient. For example, the outer- 
most row of rivets in crowfoot staying (Fig. 45, page 152) 
may be at a distance a 9 from the dotted line; for i|- inch stay- 
rods <? 2 = 3.8 inches. 

The method of staying selected consists of channel-bars 
riveted to the head and supported by through-stays; the 
upper channel-bar is assisted by an angle-iron. The channel- 
bars selected are six inches wide, and the horizontal rows of 
rivets in each bar are 3J inches apart, which brings them as 
near the flanges of the bar as they can be driven. The mid- 
dle of the lower channel-bar is 5§ inches above the top of the 
tubes, so that the lowest row of rivets is 

5t-iX 3i = 4 

inches above the top row of tubes. But the plate cannot be 
properly considered to be rigidly supported at a line drawn 
through the tops of the tubes; we will assume the line of 
support to be a fourth of the diameter lower down. This 
makes a space of 4} inches, instead of the 4.55 inches calcu- 
lated for 13/16 rivets. The excess may be considered to be 
offset by the fact that the other row of rivets in the channel- 
bar is only 3-J- inches distant. 

The upper channel-bar is placed 8 inches above the lower 
one, so that the stay-rods are 

3 o-(6J+5f+8) = 9i 

inches below the shell. If these upper rods are much less 
than 10 inches from the shell access to thcboiler will be diffi- 
cult. The space immediately above the upper channel-bar is 
stayed by aid of an angle-iron which is riveted to the channel- 
bar. 

The distance of the lower row of rivets in the upper chan- 
nel-bar, above the upper row in the lower bar, is 

8 - 3i = Al 



BOILER DESIGN. 34/ 

inches — the same as the distance assigned to the lowest row 
of rivets above the assumed line of support at the top row of 
tubes. The top row of rivets in the angle-iron is only a 
little more than four inches below the dotted boundary-line. 
Lower Stay-rods. — In order to determine the load carried 
by the lower stay-rods, we will assume that half the load on 
the plate between the lowest row of rivets and the top row of 
tubes is carried by the rivets, and that the load on the plate 
between the channel-bars is divided equally between them. 
Now we have assumed that the line of support at the tubes is 
a quarter of their diameter below their tops, and have found 
this line to be 4f inches below the lowest row of rivets. Half 
of 4! is 2-f. Again, the distance between the top row of rivets 
in the lower channel-bar and the bottom row in the upper 
bar is 4f inches, of which half is 2-f. The distance apart of 
the two rows of rivets in the channel-bar is 3J- inches. The 
total width of plate supported by the channel-bar may there- 
fore be considered to be 

2 f + 3i+ 2 f = 8 inches. 

The length of the lower channel-bar at the middle is 52 
inches, as measured on Fig. 142 ; but it is convenient to space 
the rods 132 inches apart, and to consider the bar to have four 
equal spaces, which leads to an assumed length of 54 inches. 

The load on the lower channel-bar is considered to be 

150 X 8 X 54 = 64,800 pounds. 

We will treat the channel-bar as a continuous girder with 
four equal spaces and five points of support, of which three 
are at the stay-rods and two are at the shell of the boiler. 
By the theory of continuous girders a uniform load on the 
channel-bar would be distributed among the five points of 
supports as follows: At each point of support at the shell 
11/112, at each outer stay-rod 32/1 12, at the middle stay-rod 
26/112. This would bring on each of the outer stay-rods 
T 3 T 2 ^ X 64,800 = 18,514 pounds. 



348 S TEA M-B OILERS. 

Now the load is not uniformly distributed, but is carried in 
part by the rivets and in part by the nuts and thick washers 
on the stay-rods; but the actual distribution will bring a less 
load on the two outer stays, so that the assumption of the 
load just found is on the side of safety, and it is conveniently 
calculated. 

If we assume 9000 pounds for the working-stress in the 
stay-rods, we may calculate the diameter by the equation 

7td* __ 18,510 
4 9000 

which gives for the diameter something less than if of an 
inch. For simplicity all five stay-rods will be the same size, 
namely, 1} of an inch — that required for the two upper stay- 
rods. This is the diameter of the body of the rod; the ends 
are enlarged to 2,\ inches where the thread is cut for the nut. 

Lower Channel-bar. — The determination of the actual 
stresses in the channel-bar, allowing for the effect of the nuts 
and thick washers on the stay-rods, is very uncertain. On the 
other hand, the application of the theory of continuous girders 
with a uniform load may not give us a stress as large as the 
actual maximum stress. We will therefore use an approxi- 
mate method, which will give a stress at least as great as the 
greatest stress in the bar. 

For this purpose we will assume that a piece of the 
channel-bar cut by the lines ab and cd (Fig. 140) may be 
treated as a simple beam. These lines ab and cd are drawn 
at one fourth of the diameter of the thick washers from the 
centre of the rod, or at 

iX 5i= if 

of an inch. We will further assume that the load on the pair 
of rivets A and B is due to the pressure of the steam on the 
area efg/i, bounded by lines drawn half-way between them 
and the nearest point of support. Thus eg is half-way 
between the rivets and the line ab, gh is half-way between the 



BOILER DESIGX, 



349 




.35° S TEA M-B OILERS. 

rivets and the line of support at the upper row of tubes, ef 
is half-way between the channel-bars, and fh is half-way to 
the next pair of rivets. The rivets are 4f inches from the 
nearest stay-rod, and are 

4i - if = 3f 

inches from the line ab\ half of this is i-J-j. of an inch. The 
two pairs of rivets are 

(I3i- 2 X 4t) = 4 
inches apart ; half of this is 2 inches. The area of efgh is 

(IH + 2)X 8 = 2 9 J 

square inches; and the steam-pressure on that area is 
29J X 150 = 442 5 pounds. 

This is the load due to each pair of rivets between a pair 
of stay-rods; and since the rivets are symmetrically placed, 
this is also the supporting force at each end of the beam. 
Between the two pairs of rivets the beam is subjected to a 
uniform bending moment, equal to the load on a pair of rivets 
multiplied by their distance from the end of the beam; that 
is, the bending moment is 

4425 X 3l= 14934. 
The theory of beams gives 

fl 

M = — , 

y 

in which M is the bending moment, / is the moment of inertia 
of the section of the beam, y is the distance of the most 
strained fibre from the neutral axis, and f is the stress at that 
fibre. For rolled-steel channel-bars we may use, for/, 16,000 
pounds, so that with the given value of M we have 

16,000/ / 

14.934 = - > or - = 0.933. 



BOILER DESIGN. 35 I 

Now / and y depend on the form and size of the section 
of the beam, and, conversely, the size and form of beam 
required may be determined from them. But as the upper 
channel-bar is exposed to a greater bending moment and con- 
sequently must have a larger section than is required for the 
lower bar, we will defer the discussion of this matter, because 
it is convenient to make the bars of the same size. 

Upper Stay-rods. — The flat surface of the boiler-head 
above the lower channel-bar is supported by the upper 
channel-bar aided by the angle-iron which is firmly riveted to 
it, and which will be assumed to act with and form a part of 
the channel-bar. 

Following our general convention that the pressure on a 
portion of the head between two lines of support is divided 
equally between them, we will assume that the load on the 
upper channel-bar is due to the steam-pressure on an area 
bounded at the bottom by a line half-way between the upper 
and lower channel-bars, and at the top by an arc 3^ inches 
inside the boiler-shell. On Fig. 140 half of this area is rep- 
resented by jkl; the arcj/c being about half-way between the 
root of the flange, shown by the outer dotted boundary line, 
and the adjacent rivets. In place of the area jkl we will take 
the rectangular area Imno, bounded at the end by a line at the 
middle of the end of the channel-bar, and at the top by a line 
mn so chosen as to make the rectangular area larger than the 
area it replaces. The width of this area, ////, is g{ inches, so 
that the load per inch of length is 

9£ X 150 = I337-5 pounds. 

The upper channel-bar may be assimilated to a continuous 
girder with three unequal spans; the middle span between 
the stay-rods is 15^ inches, and the end spans between the 
stay-rods and the roots of the flange of the head are each 
11J inches. This makes the end spans nearly 3/4 of the 
middle span. Now, a continuous girder uniformly loaded 



3 5 2 S TEA M-B OILERS. 

with w pounds per inch of length, which has a middle span / 
inches long, and two end spans f / inches long, will have for 
the end-supporting forces ff}«//, and for the middle support- 
ing forces f|-Jtt>/. The end supporting forces are provided 
by the shell, which is abundantly able to carry them. The 
stay-rods, which furnish the middle-supporting forces, must 
each carry 

Ui X J 5i X I387-5 = 21,083 pounds. 

Assuming a working-stress of 9000 pounds per square inch 
for the stay, the area of the section for a stay is 

21,083 -T- 9000 = 2.34 



square inches. The corresponding diameter is not quite li-|- 
of an inch. As rods of this size are not regularly carried in 
stock, we will take the next larger regular size, namely, if 
of an inch. This is the size mentioned in connection with the 
discussion of the lower stay-rods. 

Upper Channel-bar. — The calculation of the stress in the 
upper channel-bar will be made by an extension of the same 
approximate method used with the lower channel-bar. Since 
the middle span is wider than the end spans, it will be suffi- 
cient to make a calculation for it only. The calculation is 
made as for a simple beam supported at the ends, the points 
of support being at one fourth of the diameter of the thick 
washer from the middle stay-rod, that is, at the distance of 
1 1 of an inch from the stay-rod. The distance between the 
upper stay-rods is 15^ inches, so that the span of the beam is 

1 Si — 2 X if = I2f- inches. 

The beam is assumed to be loaded with concentrated loads 
applied at the rivets C, D, E, F> G, and H (Fig. 140); the 
load on the rivet / is assumed to be carried by the stay-rod 
directly, and is not included in this calculation. The pair of 



BOILER DESIGN. 353 

rivets D and B, and the several rivets C, G, and If, are 
assumed to carry the load due to the pressure on the areas 
marked off by the dotted lines on Fig. 140, each line being 
drawn half-way between adjacent supporting points, except 
that the arc at the top is drawn 3] inches from the shell, as 
already said. The calculation of the loads on these rivets, of 
the supporting forces, and of the bending moments is simple 
and direct, but is tedious when stated in detail. We will 
therefore be contented to say that the bending moment at 
the middle of the beam is 37,390. Taking, as with the lower 
channel-bar, a working-stress of 16,000 pounds, we have 

16,000/ / 

37>39° = -— - — 1 or -= 2 - I 7- 

y y 

The makers of steel beams, channel-bars, and angle-irons 
publish handbooks which give the sizes and properties of the 
standard forms, including the moment of inertia / and the 

ratio — , which is called the moment of resistance. From such 

y 

a handbook it appears that the moment of resistance of the 
channel-bar 6" X 2 J" X \" is 1.08, and that the moment 
of resistance of the 3!" X 3" angle-iron is 1.55; the sum 
2.63 is larger than the required moment of resistance given 
above. These forms are consequently used as shown on 
Plate I. 

Brackets. — The boiler shown on Plate I is supported on 
four cast-iron brackets, each of which is 10 inches wide in the 
direction of the length of the boiler, and 15J inches long 
measured circumferentially. Each bracket is riveted to the 
shell by nine rivets 15/16 of an inch in diameter. Boilers 
over 16 feet long commonly have six brackets. The brackets 
are made wide and long in order that the local strains due to 
carrying the weight of the boiler may not be excessive. The 
rivets are larger than are used about the boiler, as the pitch is 
not restricted as in a calked seam. 



354 STEAM-BOILERS 

The brackets are set above the middle line of the boiler 
so that the flanges may be protected by brickwork. In the 
case in hand they are 3f inches above the middle; as much 
as 4J inches is commonly used. 

The brackets are arranged so that the weight of the boiler 
and accessories is equally divided among them, and so that 
there is as little bending-moment as possible on the shell of 
the boiler. When four brackets are used they may be some- 
what less than, a fourth of the length of a tube, from the tube- 
plat^ 

The load on the brackets may be estimated by calculating 
the weight of the boiler when entirely full of water, and add- 
ing the weight of all parts that are supported by the boiler, 
such as pipes, valves, and brickwork or covering, that may 
rest on the boiler. One fourth of this load is assigned to each 
bracket. This load on a bracket should be uniformly dis- 
tributed over the bearing-surface of the flange, which is com- 
monly 8 or 9 inches wide. But to guard against the effect of 
unequal bearing, it is well to assume the bracket to bear near 
the outer edge — say two inches from the edge. Such an 
assumption will bring the bearing-force on a bracket on 
Plate I, 10 inches from the shell. This bearing-force tends 
to rotate the bracket about its upper edge, and this tendency 
is resisted by the rivets under the flange, which must be large 
enough to resist the resulting pull on them. The other rivets 
are added to give sufficient resistance to shearing all the 
rivets. There are seldom less than nine rivets in a bracket, 
all as large as those below the flange, even though fewer would 
suffice. The bracket is usually made of cast iron, and the 
dimensions are commonly controlled as much by the condi- 
tions required for a sound casting as by calculations for 
strength. The strength may be calculated, treating it as a 
cantilever, allowing for the web connecting the flange to the 
body of the casting. 

Specifications and Contract. — The engineer intrusted 



BOILER DESIGN. 



355 



with the design of a boiler prepares a set of working drawings 
and a set of specifications which give all necessary instructions 
concerning the material to be used and the methods of con- 
struction to be followed. The drawings and specifications 
form a part of the contract with the boiler-maker. 

Boiler-makers commonly design standard forms of boilers, 
and in answer to inquiry will furnish a statement or set of 
specifications for a desired boiler in form of a letter, which 
letter forms the contract for the boiler. On the next page is 
given the contract and specifications for the boiler shown on 
Plate I. 



356 



STEAM-BOILER. 



IRON WORKS CO. 



Boston, Mass. , Feb. /, 1897. 



Gentlemen : 



Your letter of received. We will build 

One (/) Horizontal Tubular Boiler. One Boiler, viz., Sixty (bo) inches diameter by 
seventeen 2/12 (/7t 2 z) feet long. Containing 84 Tubes 3 inches diameter, by sixteen (ib) feet 
long. Shell of Boiler of O. H. Fire-box Steel, 7/16" thick, not less than 55,000 nor over 60,000 
lbs. Tensile Strength. Not less than 56% reduction 0/ area, and 25% elongation in 8" . 

Heads of Boiler of O.H. Flange Steel q/ib" thick. Longitudinal Seams Butt Jointed, 
with double covering-plates, Triple Riveted. Rivet-holes drilled in place, i.e., Rivet-holes 
punched 1/4" small, courses rolled up, covering-plates bolted on courses. Heads in courses 
with all holes together perfectly /air. Then rivet-holes drilled to full size. 

Longitudinal braces without welds, with upset screw ends. 

Two (2) or three (3) Lugs on each side, and to be provided with wall-plates and expan- 
sion-rolls. Manhole (internal frame) on top. This frame a steel casting. 



Two (2) 5" Nozzles on top, 



A Hand-hole in each head, Fusible Safety Plug in back head. Bottom at back end 

reinforced and tapped for 2" blowout 

Internal Feed Pipe placed in Boiler Co.'s style, 

With Boiler, Castings for setting, viz.; C. I., Overhung Front, Mouth-pieces, 
Division Plates, Grate Bars, shaking pattern bo" X bo" . Grate Bearers, Ash-pit Door for 
the brickwork, Back Return Arched T Bars, the Anchor Bolts for Front. One (1) set of 

six (6) Buckstaves and Tie Rods with the boiler. With the Boiler One (\) 4" Pop 

Safety Valve, (3)3/4" Gauge Cocks, One (1) 6" Steam Gauge, One (1)3/4" Water Gauge and 

One (1) Combination Column Boiler tested 225 lbs. per 

square inch. Inspected and Insured in the sum of $400.00 for one year, by Steam 

Boiler Inspection & Insurance Co 

The Boiler Castings and Fixtures as herein specified by name, delivered F. O. B. cars, 
or at vessel's wharf, or on sidewalk of building, Boston, Mass., for the sum of six hundred 
and seventy $70.00) dollars net. 

Very respectfully yours, 

IRON WORKS CO. 

P. S. — Specimens will be furnished, one lengthwise and one crossivise, from each plate. 
To be at least 18" long and planed on edge 1" or i\" wide. These specimens shall show n& 
blowhole defects and shall bend double cold, at a red heat, and at a flanging heat. 



APPENDIX. 



358 



APPENDIX. 
LOGARITHMS. 



Nat. 
Nos. 




















Proportional Parts. 





1 


2 


3 


4 


5 


6 


7 


8 


9 




1 


7404 




















12 3 


4 5 6 


7 8 9 


55 


7412 


74i9 


7427 


7435 


7443 


745i 


7459 


7466 


7474 


122 


3 4 5 


5 6 7 


56 


74S2 


7490 


7497 


7505 


7513 


75207528 


7536 


7543 


755i 


1 2 2 


3 4 5 


5 6 7 


57 


7559 


7566 


7574 


7582 


7589 


759717604 


7612 


7619 


7627 


1 2 2 


3 4 5 


5 6 7 


58 


7634 


7642 


7649 


7657 


7664 


7672 7679 


7686 


7694 


7701 


112 


3 4 4 


5 6 7 


59 


7709 


7716 


7723 


773i 


7738 


7745 


7752 


7760 


7767 


7774 


112 


3 4 4 


5 6 7 


60 


7782 


7789 


7796 


7803 


7810 


7818 


7825 


7832 


7839 


7S46 


1 1 2 


3 4 4 


5 6 6 


61 


7853 


7860 


7868 


7875 


7882 


7889 


7896 


7903 


7910 


79 J 7 


112 


3 4 4 


5 6 6 


62 


79 2 4 


793i 


7938 


7945 


7952 


7959 7966 


7973 


7980 


7987 


112 


3 3 4 


5 6 6 


63 


7993 


8000 


8007 


8014 


302I 


802818035 


S041 


8048 


S055 


112 


3 3 4 


5 5 6 


64 


S062 
S129 


3o6g 
8136 


8075 


8082 


8089 


8096 


8102 


8109 
S176 


8116 


S122 


112 


3 3 4 


5 5 6 


65 


8142 


8149 


8156 


8162 


8169 


8182 


S189 


1 1 2 


3 3 4 


5 5 6 


66 


819=; 


8202 


8209 


S215 


8222 


8228 


8235 


8241 


8248 


8254 


112 


3 3 4 


5 5 6 


67 


S261 


8267 


8274 


8280 


8287 


8293 


8299 


8306 


8312 


8319 


112 


3 3 4 


5 5 6 


68 


S325 


833i 


8338 


8344 


8351 


8357 


8363 


8370 


8376 


8382 


112 


3 3 4 


4 5 6 


69 


3388 


8395 


8401 


8407 


S4I4 


8420 


S426 


8432 


8439 


8445 


112 


2 3 4 


4 5 6 


70 


8451 


8457 


8463 


8470 


8476 


8482 


848S 


8494 


8500 


S506 


112 


2 3 4 


4 5 6 


71 3513 


S519 


8525 


8531 


8537 


8543 


8549 


8555 


8561 


8567 


112 


2 3 4 


4 5 5 


72 


8573 


8579 


8585 


S591 


8597 


8603 


S609 


861s 


8621 


S627 


I I 2 


2 3 4 


4 5 5 


73 


8633 


S639 


8645 


S651 


8657 


S663 8669 


8675 


S681 


S686 


112 


2 3 4 


4 5 5 


74 


S692 

875i 


S698 
S756 


8704 
8762 


S710 

876S 


S7I6 


8722 


8727 


S733 


8739 


S745 


112 


2 3 4 


4 5 5 


75 


8774 


8779 


8785 


8791 


8797 


8802 


I I 2 


2 3 3 


4 5 5 


76 


8S08 


3814 


8820 


882=; 


8831 


8837 8S42 


8848 


SS54 


8859 


I I 2 


2 3 3 


4 5 5 


77 


8865 


88 7 1 


SS76 


S882 


88S7 


889318899 


8904 


S910 


8915 


112 


2 3 3 


4 4 5 


78 


8921 


3927 


8932 


893S 


8943 


89498954 


S960 


8965 


8971 


112 


2 3 3 


4 4 5 


79 


S976 


8982 


8987 


8993 


8998 


9004 9009 


9015 


9020 


9025 


I I 2 


2 3 3 


4 4 5 


80 


9031 


9036 


9042 


9047 


9053 


9058^063 


9069 


9074 


9079 


112 


2 3 3 


4 4 5 


81 


90S5 


9090 


9096 


9101 


9106 


91129117 


9122 


9128 9133 


I I 2 


2 3 3 


4 4 5 


82 


9 T 3S 


9M3 


9149 


9154 


9159 


91659170 


9175 


9180 9186 


112 


2 3 3 


4 4 5 


83 


9191 


9196 


9201 9206 


9212 


9217:9222 


9227 


9232 


9238 


1 1 2 2 3 3 


4 4 5 


84 


9243 
9294 


9248 
9299 


9253 
9304 


925S 
9309 


9263 

9315 


92699274 
9320 9325 


9279 


9284 


9289 


1 1 2 2 3 3 


4 4 5 


85 


9330 


9335 


9340 


1 1 2 ! 2 3 3 4 4 5 


86 


9345 


935o 


9355 936o 


9365 


93709375 


93809385 


9390 


1 1 2 2 3 3 4 4 5 


87 


9395 


9400 


94059410 


9415 


9420.9425 


9430 9435 


9440 


Oil 


223 


3 4 4 


88 


9445 


945o 


9455 946o 


9465 


9469 ! 9474 


94799484 


9489 


Oil 


223 


3 4 4 


89 


9494 


9499 


9504 9509 


9513 


95189523 


9528 


9533 


953S 


Oil 


223 


3 4 4 


90 


9542 


9547 


9552 


9557 


9562 


95669571 


9576 


958i 


9586 


1 1 


223 


3 4 4 


91 


959° 


9595 


9600 


9605 


9609 


9614 


9619 


9624 


9628 9633 


Oil 


2 2 3 


3 4 4 


92 


963S 


9643 


9647 


9652 


9657 


9661 


9666 


9671 


9675 968c 


1 1 2 2 3 


3 4 4 


93 


96S5 


9689 


96949699 


9703 


97oS 


97i3 


9717 


97229727 


1 1 2 2 3J 2 


94 


9731 


9736 


9741 9745 


9750 


9754 


9759 


9763 


9768 


9773 


1 1 


2 2 3I 3 4 4 

1 


95 


9777 


9782 


97869791 


9795 


9800 


9805 


9809 


9ST4 


9S18 


Oil 


223 


3 4 4 


96 


9823 


9S27 


9832 9836 


9S41 


9845 


9850 


985498599863 


Oil 


223 


3 4 4 


97 


9868 


9872 


9877 9881 


9886 


9890 


9894 


9899 9903 990S 


1 1 


223 


3 4 4 


98 


9912 


9917 


9921(9926 


9930 


9934 


9939 


9943 9948,9952 


Oil 


223 


3 4 4 


99 


9956 


9961 


996519969 


9974 


9978 9983 


9987I9991I9996 


Oil 


223 


3 3 4 



APPENDIX. 
LOGARITHMS. 



359 



Nat. 

Nos. 






















Proportional Parts. 





1 


2 


3 


4 


5 


6 


7 


8 


9 
















oooo 


0043 


00S6 


0128 


0170 


0212 










1 2 


3 


4 


5 


6 


7 


8 9 


10 


0253 


0294 -)334 0374 


4 S 


12 


17 


2 i 


2 = 


29 


33 37 


11 


0414 


0453 


04920531 


0569 


0607 


0645 


0682 0719 0755 


4 8 


1 1 


'5 


19 


23 


26 


30 34 


12 


0792 


0S2S 


0864 0899 


0934 


0969 


1004 


103S 1072 1 106 


3 7 


10 


M 


'7 


21 


24 


28 31 


13 


1 1 3Q 


1173 


1 2( )l - 


1239 


1271 


1303 


1335 


[367 [399 [430 


3 6 


10 


[3 


16 


ig 


23 


26 29 


14 


1461 


1492 


1523 


1553 


1584 


1614 


1644 


[673 


1703 1732 


3 6 


9 


12 


15 


[8 


21 


24 27 


15 


1761 


1790 


I8l8 


1S47 


1875 


1903 


193' 


1959 


19S7 2014 


3 6 


8 


11 


14 


17 


20 


22 25 


16 


2041 


206S 


2095 2122 


214s 


2175 2201 


2227 


2253 2279 


3 5 


8 


1 1 


13 


16 


18 


21 24 


17 


2304 


2330 


2355 2 3 SO 


2405 


24302455 


24S0 


2504 2520 


2 5 


7 


10 


12 


*5 


17 


20 22 


18 


2553 


2577 


260] 2625 


264S 


2672 2695 


271S 


2742 2765 


2 5 


7 


9 


12 


14 


16 


19 21 


19 


27^- 


2S10 


28332856 


2S7S 


2900 2923 


2945 


2967 '29S9 


2 4 


7 


9 


II 


13 


[6 


18 20 


20 


3010 


J032 


3054 3075 


3096 


31183*39 


3160 


3181 3201 


2 4 


6 


8 


I I 


13 


'5 


17 19 


21 


3222 


V-M3 


3263 


3284 


3304 


3324 3345 


33 f >5 


33S5 3404 


2 4 


6 


8 


K) 


12 


'4 


16 18 


22 


3424 


3444 


3464 


34S3 


3502 


3522 354i 


356<>35793598 


2 4 


6 


8 


K) 


12 


14 


15 17 


23 


3617 


3636 


3655 


3674 


3692 


3711 3729 


3747 


3766 37S4 


2 4 


6 


7 


9 


1 1 


'3 


15 i7 


24 


3S02 


3820 


3338,3856 


3S74 


3S92 3909 


3927 


3945 3962 


2 4 


5 


7 


9 


1 1 


12 


14 i() 


25 


3979 


3997 


4OI4 403I 


4048 


4065 


40S2 


4099 


41164133 


2 3 


c 


7 


9 


10 


12 


14 15 


26 


4150 


4166 


418342OO 


4216 


4232 


4249 


4265 


4281 4298 


2 3 


5 


7 


8 


10 


11 


13 15 


27 


4314 


4330 


4346 4362 


437S 


4393 


4409 


442544404456 


2 3 


5 


6 


S 


9 


1 1 


13 14 


28 


4472 


44S7 


45024518 


4533 


454S 4564 


4579 


4594 4609 


2 3 


5 


6 


8 


9 


1 1 


12 14 


29 


4624 
477i 


4639 
47S6 


4654 4660 


4683 


469S 
4843 


4713 


4728 


4742 4757 


1 3 


4 


6 


7 


9 


10 


12 13 


30 


4S0O 4S14 


4829 


4S57 


4S71 


4886 4900 


1 3 


4 


6 


7 


9 


10 


11 13 


31 


49M 


492S 


4942 405 ^ 


4969 


49834997 


501T 


5024 503S 


r 3 


4 


6 


7 




10 


11 12 


32 


5051 


5065 


5079 5092 


5105 


5 IK, 5132 


5M5 


5159 5172 


1 3 


4 


5 


7 


8 


9 


n 12 


33 


5185 


519S 


5211 5224 


5237 


5250 5263 


5276 


5289 5302 


1 3 


4 


5 


6 


8 


9 


10 12 


34 


5315 


532S 


5340 5353 


5366 


53785391 


5403 


54i6 542S 


1 3 


4 


5 


6 


8 


9 


10 11 


35 


544i 


5453 


5465^478 


5490 


5 502 5 514 


5527 


5539 555^ 


r 2 


4 


5 


6 


7 


( i 


10 11 


36 


5563 


5575 


5587 5599 


5611 


5623 5635 


5647 


565SJ5670 


r 2 


4 


5 


6 


7 


8 


10 11 


37 


5682 


5694 


5 70- 5717 


5729 


5740 5752 


5763 5775 5 7S<» 


1 2 


3 


5 


6 


7 


8 


9 10 


38 


579 s 


5S09 


5S21 5S32 


5S43 ; 5S?= 5866 


5877 


5888:5899 


1 2 


3 


5 


6 


7 


8 


9 10 


39 591 1 


5922 


5933 5944 


5955 


5966 5977 


5988 


5999 6010 


1 2 


3 


4 


5 


7 


S 


9 10 


40 


6021 




6031 


6042 6053 


6064 


6075 6085 


6096 


6107 6117 


1 2 


3 


4 


5 


6 


T 


9 10 


41 


612S 


613S 


6149 6160 


6170 


6180 6191 


6201 


6212 6222 


1 2 


3 


4 


5 


6 


7 


8 9 


42 


6232 


6243 


6253 6263 


6274 


62S4 6294 


6304 


6314 6325 


1 2 




4 


5 


6 


7 


8 9 


43 


6335 


6345 


63556365 


6375 


63856395 


6405 


64i5'6425 


1 2 


3 


4 


5 


6 


7 


8 9 


44 


6435 


6444 


64546464 


6474 


64S46493 


6503 


65136522 


1 2 


3 


4 


5 


6 


7 


8 9 


45 


6532 


6542 


6551 6561 


6571 


6580 6590 


6599 


6609 661 S 


1 2 


3 


4 


5 


(» 


7 


8 9 


46 


6628 


6637 


66466656 


6665 


6675 6684 


6693 


6702 6712 


1 2 


3 


4 


5 


6 


7 


7 8 


47 


6721 


6730 


67396749 


6758 6767 0776 


6785 


6794 6S03 


1 2 


3 


4 


5 


5 


6 


7 S 


48 


6S12 


6S21 


6S30 6839 


6848 6857 6866 


6S7^ 


68S46S93 


1 2 


3 


4 


4 


5 


6 


7 8 


49 


6902 


691 1 


6920 692S 


6937 69466955 


6964 


6972 6981 


1 2 


3 


4 


4 


? 


6 

7 


7 S 


50 


6990 


699S 


7007 


7016 


7024 


7033 


7042 


7050 


70597067 


r 2 


3 


3 


4 


5 


7 8 


51 


7076 


7084 


7093 


7101 


7110 


7118 


7126 


7135 


7M3 7152 


1 2 


3 


3 


4 


5 


6 


7 8 


52 


7160 


716S 


7177 


7185 


7193 


7202 


7210 


7218 


7226 7235 


1 2 


2 


3 


4 


^ 


6 


7 7 


53 


7243 


7251 


7259 


7267 


727- 72S4 


7292 


7300 


7303 7316 


1 2 


2 


3 


4 


5 


6 


6 7 


54 


7324 7332' 7340 


734S 


7356!7364 7372 


738o 


738SI7396 


1 2 


2 


3 


4 


5 


6 


6 7 



300 APPENDIX. 

Explanation of the Table for Finding the Area of 
Segment of a Circle. — The areas given in the table are for 
a circle I inch in diameter. The diameter is divided into 
iooo parts, and the area for segments of different heights can 
be taken directly from the table, since the ratio of the height 
of the segment to the diameter of the circle is the same as 
the height of the segment. 

For a circle whose diameter is other than unity. Given 
the diameter of the circle and the height of segment. Re- 
quired area of segment. Divide height of segment by diameter ; 
find area given in the table opposite this ratio ; multiply this 
area by the square of the diameter and the result is the re- 
quired area. 

Example. — Dia. of circle = 6o n ', height of segment = 18". 

1 8 -f- 60 = . 30 ; area in table opposite .30 is .19817. 
.19817 X 60 X 60 = area of segment = 713.4 sq. in. 

Given the diameter of the circle and the area of a segment, 
to find the height. 

Divide the area of the segment by the square of the diam- 
eter. Find in the table the area nearest to this, multiply 
the ratio corresponding to this by the diameter of the circle, 
and the result is the required height of the segment. 

Example. — Area of segment = 713.4 sq. in. 

Diameter of circle = 60" '. Required the height of the 
segment. 

71 3.4 
— = .19817. Ratio opposite this is .300. 

.300 X 60" = 18", the required height. 

Example — Area of segment == 640 sq. in. 
Diameter of circle = 50". 

640 



= .2560; nearest ratio, .362. 



50 X 50 

.362 X 50 = 18.10", the required height. 



APPENDIX. 361 

TABLE FOR FINDING AREAS OF SEGMENTS OF A CIRCLE. 



<-> V 




*i v 




«-i 4) 


j 


~ O V 




«o«J 




•G «->T. 


c 


■C-M — 


c 


J3«7, 


c 


1 JZ - — 


c 


£*"- 




bo^ t 


u 


bc w « 


<u 


W>^ £ 


a 

bo 
u 
to 


bo y 


u 


"^ u 


01 


'5 Crj 

<♦< bo . 


a 

bo 

4) 


'3 cf. 


a 

bo 
u 

C/5 


"rr bo . 




a 

be 
u 

CO 


KB* 


a 

bo 
<u 

C/J 


O hj g 


"o 






O <L> c 

2 w .i 




v a 
2^1 


a! 


m 




doQ 


<L> 


SoQ 


<u 


SoQ 


u 


rtoQ 




* oQ 




K 


< 


Pi 


< 


tf 


< 


Oi 


< 


£ 


< 


.210 


.11990 


.260 


. 16226 


• 310 


.20738 


.360 


•25455 


.410 


.30319 


1 


. 12071 




.16314 


1 


. 20830 


I 


•25551 


1 


•30417 


2 


.12153 


■ 


.16402 


2 


.20923 


2 


•25647 


2 


.30516 


3 


.12235 


3 


.16490 


3 


.21015 


3 


•25743 


3 


•306.4 


4 


.12317 


4 


.16578 


4 


.21108 


4 


•25839 


4 


.3071a 


.215 


.12399 


• 265 


.16666 


•315 


.21201 


.365 


•25936 


•415 


.30811 


6 


.12481 


6 


•16755 


6 


.21294 


6 


.26032 


6 


■30910 


7 


.12563 


7 


.i63 43 


7 


•21387 


7 


.26128 


7 


.31008 


8 


.12646 


8 


.16932 


8 


.21480 


8 


.26225 


8 


.31107 


9 


.12729 


9 


. 1 7020 


9 


■21573 


! 9 


.26321 


9 


.31205 


.220 


.12811 


.270 


.17109 


.320 


.21667 


•37o 


.26418 


.420 


•31304 


1 


.12894 


1 


.17198 


1 


. 2 I 760 


1 


•26514 


1 


■3 T 4°3 


2 


.12977 


2 


.17287 


2 


.21853 


2 


.26611 


2 


•31502 


3 


. 1 3060 


3 


.17376 


3 


•21947 


3 


. 26708 


3 


. 3 1 600 


4 


•I3M4 


4 


•17465 


4 


. 22040 


4 


.26805 


4 


•31699 


.225 


.13227 


•275 


•17554 


.325 


.22134 


•375 


.26901 


•425 


.31798 


6 


.13311 


6 


.17644 


6 


.22228 


6 


.26998 


6 


•31897 


7 


•13395 


7 


■17733 


7 


.22322 


7 


.27095 


7 


.31996 


8 


.13478 


8 


.17823 


8 


.22415 


8 


.27192 


8 


•32095 


9 


.13562 


9 


.17912 


9 


.22509 


9 


.27289 


9 


•32194 


.230 


.13646 


.280 


.18002 


•33o 


.22603 


.380 


.27386 . 


•430 


•32293 


1 


•I373I 


1 


.18092 




.22697 


1 


.27483 




•32392 


2 


.13815 


2 


.18182 


2 


.22792 


2 


.27580 


2 


•3249 1 


3 


.13900 


3 


.18272 


3 


.22886 


3 


.27678 


3 


.32500 


4 


.13984 


4 


.18362 


4 


.22980 


4 


•27775 


4 


.32689 


•235 


.14069 


.285 


.18452 


•335 


•23074 


.385 


.27872 


■435 


•32788 


6 


.14154 


6 


.18542 


6 


•23169 


6 


.27969 


6 


.32887 


7 


•M239 


7 


.18633 


7 


.23263 


7 


.28067 


7 


•32987 


8 


■14324 


8 


.18723 


8 


•23358 


8 


.28164 


8 


•33oS6 


9 


.14409 


9 


.18814 


9 


•23453 


9 


.28262 


9 


•33185 


.240 


.14494 


.290 


.18905 


•34o 


•23547 


•39o 


•28359 


•440 


•33284 


1 


.14580 


1 


.18996 


1 


.23642 


1 


•28457 




•33384 


2 


.14666 


2 


.19086 


2 


■23737 


2 


•28554 


2 


•33483 


3 


.14751 


3 


.19177 


3 


■23832 


3 


.28652 


3 


.33582 


4 


• I 4837 


4 


.19268 


4 


•23927 


4 


.28750 


4 


.33682 


•245 


.14923 


•295 


• 19360 


•345 


.24022 


•395 


.28848 


•445 


•33781 


6 


.15009 


6 


•I945I 


6 


.24117 


6 


.28945 


6 


.33880 


7 


.15095 


7 


•19542 


7 


.24212 


7 


•29043 


7 


■3398o 


8 


.15182 


8 


•19634 


8 


.24307 


8 


.29141 


8 


• 34079 


9 


.15268 


9 


.19725 


9 


•24403 


9 


.29239 


9 


•34179 


.250 


•'53S5 


.300 


.19817 


•350 


.24498 


.400 


•29337 


•450 


•34278 


1 


•15441 


1 


.19908 


1 


•24593 


1 


•29435 


1 


•34378 


2 


.15528 


2 


. 20000 


2 


.24689 


2 


•29533 


2 


•34477 


3 


.15615 


3 


.20092 


3 


.24784 


3 


.29631 


3 


•34577 


4 


.15702 


4 


.20184 


4 


.74880 


4 


.29729 


4 


.34676 


.255 


.15789 


•305 


.202/6 


•355 


.24076 


.405 


.29827 


•455 


•34776 


6 


.15876 


6 


.20368 


6 


.2507I 


6 


.29926 


6 


•34876 


7 


.15964 


7 


. 20460 


7 


•25167 


7 


.30024 


7 


•34975 


8 


.16051 


8 


■20553 


8 


.25263 


8 


.30122 


8 


•35075 


9 


.16139 


9 


. 20645 


9 


•25359 


9 


.30220 


9 


•35175 



362 



APPENDIX 



NATURAL TRIGONOMETRIC 
FUNCTIONS. 



CIRCLES 



Deg. 


Sine. T 


angent. 


Cot. 


Cos. 


Deg. 





.0000 


.OOOO 


Infinite 


I. OOOO 


90 


I 


■OI75 


OI75 


57230 


.9998 


89 


2 


•0349 


0349 


28.636 


•9994 


88 


3 


•O523 


0524 


19.081 


.9986 


87 


4 


C698 


0699 


14.301 


.9976 


86 


5 


.0872 


0875 


11.430 


.9962 


85 


6 


•IO45 


1051 


9.5M4 


•9945 


84 


7 


. 1219 


1228 


8.1443 


.9925 


83 


8 


.1392 


I405 


7.II54 


•9903 


82 


9 


.1564 


I5S4 


63138 


.9S77 


81 


10 


.1736 


1763 


5.67I3 


.9848 


80 


11 


.1908 


1944 


5.1446 


.9816 


79 


12 


.2079 


2126 


4.7046 


.9781 


78 


13 


.2250 


2309 


4.3315 


• 9744 


77 


J 4 


,2419 


2493 


4.010S 


•9"03 


76 


15 


.2588 


2679 


3-7321 


• 9 6 59 


75 


16 


.2756 


2867 


3.4874 


.9613 


74 


17 


.2924 


3057 


3.2709 


.9563 


73 


18 


.3090 


3249 


3.0777 


•95ii 


72 


19 


.3256 


3443 


2.9042 


•9455 


7i 


20 


.3420 


3640 


2-7475 


•9397 


70 


21 


.3584 


3S39 


2.6051 


.9336 


69 


22 


•3746 


4040 


2.4751 


.9272 


68 


23 


•3907 


4245 


2-3559 


.9205 


67 


24 


.4067 


4452 


2.2460 


•9135 


66 


25 


.4226 


4663 


2.144 5 


.9063 


65 


26 


•4384 


4877 


2.0503 


.89SS 


64 


27 


.4540 


5095 


1.9626 


.8910 


63 


2S 


.4695 


53'7 


1.8807 


.8829 


62 


29 


.4S48 


5543 


1 S040 


.87-16 


61 


30 


.50OO 


5774 


1.7321 


.8660 


60 


31 


.5I50 


6009 


1.6643 


.8572 


59 


32 


.5299 


6249 


1.6003 


.8480 


58 


33 


.5446 


6494 


1-5399 


.8387 


57 


34 


•5592 


6745 


1.4826 


.8290 


56 


35 


•5736 


7002 


1. 4281 


.8192 


55 


36 


•5S7S 


7265 


I.3764 


.8090 


54 


37 


.6018 


7536 


1.3270 


.79S6 


53 


38 


•6i57 


7813 


1.2799 


.7880 


52 


39 


.6293 


8098 


1.2349 


• 7771 


51 


40 


.642S 


8391 


1.1918 


.7660 


50 


4i 


.6561 


8693 


1. 1504 


•7547 


49 


42 


.6691 


9004 


1 . 1 1 06 


•7431 


48 


43 


.6S20 


9325 


1.0724 


•7314 


47 


44 


.6947 


9°57 


I.0355 


•7193 


46 


45 


.7071 1 


0000 
Cot. 


1 . 0000 
Tangent. 


.7071 
Sine. 


45 


Deg. 


Ccs. 


Deg. 



Diam. 


Circumf. 


Area, 


Inches. 


Inches. 


Sq. In. 


12 


371 


H3i 


14 


44 


i54 


16 


50i 


201 


18 


56i 


254I 


20 


621 


3M^ 


22 


69i 


3 So| 


24 


751 


452f 


26 


8if 


531 


28 


88 


6i5f 


30 


94i 


7o6f 


32 


icoi- 


8o 4 i 


34 


106I 


907I 


36 


**3l 


1017I- 


38 


Ii9f 


"34$ 


. 40 


I25f 


1256I 


42 


132 


13S5I 


44 


13S} 


15201 


46 


144^ 


i66i| 


48 


1 5o| 


1809^ 


50 


J 57| 


1963I 


52 


163I 


2I23f 


54 


169I 


2290^ 


56 


x 75| 


2463 


58 


1821 


2642I- 


60 


i88i 


2827! 


62 


i94f 


3019^ 


64 


201 


3217 


66 


207I 


342ii 


68 


213I 


5631! 


70 


2 ^9| 


3848^ 


72 


2261 


40711 


74 


232! 


43C04 


76 


2 3 8f 


4:36* 


78 


245 


4778I 


80 


2511 


5026I 


82 


257f 


5281 


84 


263^ 


554if 


86 


2701- 


5So8| 


88 


276^ 


6082^ 


90 


2S2| 


6 3 6if 


92 


289 


6647I 


94 


295l 


6939! 


96 


3orf 


7^38* 


9 S 


307^ 


7543 


100 


3 Mi 


7854 


102 


32of 


8171* 



APPENDIX. 
ROUND RODS OF WROUGHT IRON. 



3^3 

















is of 








Weight 


Diameter 


I >iameter 




Effective 


Diameter 
in Inches. 


Circumfer- 
ence 
in Inches. 


Area in 
Sq. Inches. 


of Rod 

One Foot 

Long. 


of Upset 
Si rew 
End. 


of Screw 
it Root ol 
Thread. 


rhreads Area of 

per Inch Sa-pvyEnd 

Nu.nl. 1 










Inches. 


Inches. 




Per Cent. 




1/16 


.1963 


.0031 


.OIO 










i/S 


.3927 


.0123 


.041 










3/16 


•5S9O 


.0276 


.092 










1/4 


.7854 


.0491 


.164 










5/16 


.9817 


.0767 


.256 










3/8 


I.1781 


. 1 104 


.368 










7/16 


1-3744 


.1503 


• 501 










1/2 


1.5708 


.1963 


.654 


3 


.620 


IO 


6f 


9/16 


I. 7671 


.24S5 


.828 


t 


.620 


IO 


2J 


5/8 


1.9635 


. 3068 


I.023 


7 


.731 


9 




11/16 


2.1598 


.3712 


1.237 


I 


•837 


8 


4b 


3/4 


2.3562 


.4418 


1.473 




.837 


8 


25 


13/16 


2.5525 


.5185 


I.72S 


T 1 

A 8 


.940 


7 


34 


7/8 


2.7489 


.6013 


2.004 


T i 


I .065 


7 


48 


15/16 


2.9452 


• 6903 


2.301 


T 1 


I .065 


7 


29 


1 


3.I416 


.7S54 


2.6l8 


If 


I . 160 


6 


35 


1/16 


3-3379 


.8866 


2.955 


If 


I. 160 


6 


19 


1/8 


3-5343 


.9940 


3-313 


jl 


I.2S4 


6 


30 


3/16 


3.7306 


1. 1075 


3.692 


J i 


I.284 


6 


17 


i/4 


3.9270 


1.2272 


4.O9I 


if 


I.389 


5i 


23 


5/i6 


4.1233 


i.353o 


4.510 


It 


I.49O 


5 


29 


3/8 


4.3197 


1.4849 


4-950 


T 3 


I.49O 


5 


18 


7/16 


4. 5160 


1.6230 


5-4IO 


T 7 
1 S 


I .615 


5 


26 


1/2 


4.7124 


1.7671 


5.890 


2 


I .712 


4i 


30 


5/8 


5-I05I 


2.0739 


6.913 


a* 


1.837 


4i 


28 


3/4 


5.4978 


2.4053 


8.018 


2i 


1 . 962 


4i 


26 


7/8 


5.8905 


2.7612 


9.204 


2f 


2.0S7 


4^ 


24 


2 


6.2832 


3.1416 


I0.47 


2i 


2.175 


4 


18 


1/8 


6.6759 


3.5466 


11.82 


2f 


2.3OO 


4 


17 
28 


1/4 


7.0686 


3.9761 


13-25 




2.550 


4 


3/8 


7.46T3 


4.4301 


14.77 


3 


2.629 


3i 


23 


1/2 


7-S540 


4.9087 


16.36 


3* 


2-754 


3i 


21 


5/8 


8.2467 


5.4II9 


18.04 


3i 


2.879 


3h 


20 


3/4 


8.6394 


5-939° 


19.80 


3f 


3.OO4 


3h 


19 
26 


7/8 


9.0321 


6.4918 


21.64 


3l 


3-225 


3i 


3 


9.4248 


7.0686 


23.56 


31 


3.317 


3 


22 



3^4 



APPENDIX. 
LAP-WELDED BOILER-TUBES. 































u 
V 




c/i 
U 


w^ 


e 


21 


Kg 




£& 


+1 u 


tt, 5J 


j 


V 


a 
3 


a 

a 

5 > 

— en 

rt Si 
c.n 


C 

«T 

4; 

c 

!5 


U _C3 
O 4) 


,1? 

OJ3 

n 

a; — 

Is 


U T 
<U C 

£co 


c 


CO <u 

1- • 

%£& 

-3_r 

-CCO rs 

*> £ 
go* 


J=CO rt 

S) £ 

go* 


X 

u - 

& 

f ^_ rt 
£ c 


C 

8.3 

si . 

C8 — 

£ c 




£ 

u 

a 

J3 

'53 


c/5 


w 


1-1 


H 


u 


U 


H 


H 


J 


hJ 


co 


CO 


I 


i 


.86 


.072 


3 J 4 


2.69 


.78 


■57 


382 


4.46 


.26 


.22 


• 71 


*H 


M 


i. ii 


.072 


3-93 


3-47 


1.23 


.96 


3 


06 


3-45 




33 


.29 


.89 


% 


\Yi 


1-33 


.083 


4.71 


4.19 


1.77 


1.40 


2 


55 


2.86 




39 


•35 


1.24 


1% 


i% 


1.56 


•095 


5-5o 


4.90 


2.40 


1. 91 


2 


18 


2-45 




46 


.41 


1.66 


2 


2 


1. Si 


• 095 


6.28 


5-6q 


3-14 


2-57 


I 


91 


2. 11 




52 


•47 


1. 91 


2^ 

2 ^ 


2*4 


2.06 


.095 


7.07 


6.47 


3-Q8 


3-33 


I 


70 


1.85 




59 


•54 


2.16 


2*£ 


2.S-8 


.109 


7-8 5 


7-17 


4.91 


4.09 


I 


53 


1.67 




65 


.60 


2-75 


2^ 


2% 


2-53 


.109 


8.64 


7-95 


5-94 


5-°3 


I 


39 


1. 51 




72 


.66 


3-04 


3,, 


^ 


2. 7 8 


.109 


9.42 


8.74 


7.07 


6.08 


I 


27 


*-37 




7 ! ^ 


•73 


3-33 


3H 


:^ 


301 


. 120 


10.21 


9.46 


8.30 


7.12 


I 


17 


1.26 




S5 


•79 


3-96 


3H 


3.26 


. 120 


11.00 


10 24 


9.62 


8-35 


I 


09 


1. 17 




92 


.85 


4.28 


3% 


3% 


3-5i 


. 120 


11.78 


11.03 


11.04 


9.68 


I 


02 


1.09 




oS 


.C2 


4.60 


4 f/ 


4 


3-73 


.134 


12-57 


11.72 


12.57 


10.94 




95 


1 .02 


1 


05 


.98 


5-47 


4*6 


4*£ 


423 


•i34 


14.14 


13.29 


15.90 


14.07 




85 


.90 


1 


18 


I. II 


6.17 


5 


5 


4.70 


.148 


I5-7I 


14.78 


19.63 


17.38 




76 


.81 


1 


3i 


1-23 


7-58 


6 


6 


567 


.165 


18.85 


17.81 


28.27 


25-25 




64 


.67 


1 


57 


1.48 


10. 16 


7 


7 


6.67 


.165 


21.99 


20.95 


38.48 


34-94 




55 


•57 


1 


83 


i-75 


11.90 


8 


8 


7.67 


.165 


25-13 


24.10 


50.27 


46.20 




48 


•50 


2 


09 


2.01 


i3-o5 


9 


9 


8.64 


.180 


28.27 


27.14 


63.62 


58.63 




42 


•44 


2 


35 


2 .26 


16.76 


IO 


IO 


9-59 


.203 


31-42 


30.14 


78.54 


72. 2Q 




38 


.40 


2 


62 


251 


20.99 


ii 


ii 


10.56 


.220 


34-56 


33-17 


95-03 


87.58 




35 


•36 


2 


SS 


2.76 


25-03 


12 


12 


"•54 


.229 


37-7o 


36.26 


113.10 


IO4.63 




32 


•33 


3 


J 4 


3.02 


28.46 



SCREW-THREADS. 

Angle of thread 6o°. Flat at top and bottom = § of pitch. 



Diameter of 


Diameter at 


Threads 


Diameter of 


Diameter at 


Threads 


Screw, 


Root of Thread. 


per Inch, 


Screw, 


Root of Thread, 


per Inch, 


Inches. 


Inches. 


No. 


Inches. 


Inches. 


No. 


-A 


.185 


20 


2 


1. 712 


4Y2 


TS 


.240 


18 


2*4 


1 .962 


* 4*6 


% 


• 294 


16 


2*£ 


2. 175 


4 


TS 


•344 


14 


2% 


2-425 


4 


V2 


.400 


^3 


3 


2.629 


3Y2 


1% 


•454 


12 


3*4 


2.879 


$& 


¥s 


•507 


11 


3Y2 


3.100 


3*4 




.620 
•731 


10 
9 


■M 


3-317 


3 








4 


3-567 


3 


1 


.837 


8 


4*4 


3-798 


2% 


l tt 


.940 


7 


\Yi 


4.028 


2 U 


*H 


1.065 


7 


4H 


4255 


2% 


1% 


1. 160 


6 














5 


4.480 


2*6 


iU 


1.284 


6 


5*4 


4 -730 


2*£ 


*% 


I-3S9 


5% 


5Y2 


5-053 


2% 


M 


1.490 


5 


sH 


5.203 


2% 


iVs 


1.615 


5 


6 


5-423 


2*4 



APPENDIX. 365 

WROUGHT-IRON WELDED STEAM-, GAS-, AND WATER-PIPE. 





Diameter. 






Transverse Areas. 


Nominal 


Number of 








:kness. 






Weight 

per 

Foot. 


Threads 
per Inch of 


Nominal 


Actual 


Thi 

Actual 


External. 


Internal. 


Internal 


External. 


Internal. 












Inches. 


Inches. 


Inches. In 


ches. 


Sq. In. 


Sq. In. 


Pounds. 




H 


•4°5 


•27 


068 


.129 


•0573 


.241 


27 


H 


.543 


•364 


088 


.229 


. 104 1 


.42 


18 


% 


.675 


•494 


091 


.358 


.1917 


•559 


l8 


\& 


.84 


• 623 


109 


•554 


.3048 


•837 


14 


H 


1.05 


.824 


113 


.866 


•5333 


1. us 


14 


1 


I -3 I S 


1.048 


i34 


1-358 


.8626 


1.668 


nH 


«H 


1.66 


1.38 


14 


2.164 


1.496 


2.244 


"^ 


ij| 


1.9 


1. 611 


M5 


2.835 


2.038 


2.678 


nH 


2 


2-375 


2.067 


i54 


4-43 


3-356 


3.609 


»fci 


2^ 


2.875 


2.468 


204 


0.492 


4-784 


5-739 


8 


3 


3-5 


3.067 


217 


9.621 


7.388 


7-536 


8 


3*6 


4- 


3.548 


226 


12.566 


9.8S7 


9.001 


8 


4 


4-5 


4.026 


237 


15.904 


12.73 


10.665 


8 


4^ 


5- 


4.508 


246 


I9-635 


15-961 


12.34 


8 


5 


5-563 


5-045 


259 


24 . 306 


19.99 


14.502 


8 


6 


6.625 


6.065 


28 


34-472 


28.888 


18.762 


8 


7 


7.625 


7.023 


301 


45.664 


38.738 


23.271 


8 


8 


8.625 


7.982 


322 


58.426 


50.04 


28.177 


8 


9 


9.625 


8-937 


344 


72.76 


62.73 


33-701 


8 


10 


10 -75 


10.019 


366 


90.763 


78.839 


40.065 


8 


11 


12 


11.25 


375 


113.098 


99 ■ 402 


45-95 


8 


12 


"•75 


12 


375 


127.677 


113.098 


48.985 


8 


T 3 


14 


13-25 


375 


1 53-938 


137.887 


53-921 


8 


M 


15 


1425 


375 


176.715 


159.485 


57 • 893 


8 


15 


16 


15-25 


375 


201.062 


182 655 


61.77 


8 




18 


1725 
19.25 
21.25 
23.25 


375 
•375 
375 
375 


254-47 
314.16 
380.134 
452 39 


233.706 
291.04 
354-657 
424-558 


69.66 
77-57 
85-47 
93-37 


















24 









WROUGHT-IRON WELDED EXTRA STRONG PIPE. 



H 


.405 


.205 


.1 


.129 


•033 


.29 


27 


H 


•54 


•294 


.123 


.229 


.068 


•54 


18 


% 


•675 


.421 


.127 


.358 


•139 


•74 


18 


% 


.84 


•542 


.149 


•554 


•231 


1. Og 


14 


1.05 


.736 


•157 


.866 


•452 


1.39 


14 . 


1 


1. 315 


•951 


.182 


1-358 


•7i 


2.17 


"^ 


& 


1.66 


1.272 


.194 


2.164 


1.271 


3 


»vl 


1.9 


1.494 


.203 


2.835 


1-753 


3-6 3 


nH 


2 


2-375 


*-933 


.221 


4-43 


2-935 


5.02 


"14 


*\b 


2.875 


2-315 


.28 


6.492 


4.209 


7-6 7 


8 


3 


3-5 


2.892 


•304 


9.621 


6.569 


10.25 


8 


3^ 


4 


3-358 


.321 


12.566 


8.856 


12.47 


8 


4 


4-5 


3-8i8 


•34i 


I5-904 


11.449 


14.97 


8 


5 


5-563 


4.813 


•375 


24.306 


18.193 


20.54 


8 


6 


6.625 


5-75 


•437 


34.472 


25.967 


28.58 


8 



366 



APPENDIX. 







HEAT 


OF THE LIQUID— 


WATER. 






Temp. 
Deg. F. 


Heat of 


Temp. 
Deg. F. 


Heat of 


Temp. 


Heat of 


Temp. 


Heat of 


Temp. 


Heat of 


Liquid. 


Liquid. 


Deg. F. 


Liquid. 


Deg. F. 


Liquid. 


Deg. F. 


Liquid. 


t 


g 


t 


4 


/ 


1 


t 


<7 


t 


1 


32 


o 


69 


37-12 


106 


74.O 


143 


III. 2 


180 


148.5 


33 


I.OI 


70 


38 II 


107 


75 


144 


112. 2 


181 


M9-5 


34 


2.01 


71 


39 " 


108 


76.0 


145 


113. 3 


182 


150.6 


35 


3 02 


72 


40.11 


109 


77.0 


146 


114.3 


183 


151. 6 


36 


4-03 


73 


41. 11 


110 


78.0 


147 


115 3 


184 


152.6 


37 


5 04 


74 


42 11 


111 


79.0 


148 


116.3 


185 


153-6 


38 


6.04 


75 


43-11 


112 


80.0 


149 


H7-3 


186 


154-6 


39 


705 


76 


44 J * 


113 


81.0 


150 


118.3 


187 


155-6 


40 


8.06 


77 


45.10 


114 


82.0 


151 


119.3 


188 


156.6 


41 


9.06 


78 


46. 10 


115 


83.0 


152 


120.3 


189 


157.6 


42 


10.07 


79 


47.09 


116 


84.0 


153 


121. 3 


190 


158.6 


43 


11.07 


80 


48.09 


117 


850 


154 


122.3 


191 


159.6 


44 


12.08 


81 


49.08 


118 


86 


155 


!23-3 


192 


160.6 


45 


13-08 


82 


50 08 


119 


87.0 


156 


124-3 


193 


161. 6 


46 


14.09 


83 


51-07 


120 


8S.1 


157 


125.4 


194 


162.6 


47 


15 09 


84 


52.07 


121 


89.1 


158 


126.4 


195 


163.7 


48 


16. 10 


85 


53.06 


122 


90.1 


159 


127.4 


196 


164.7 


49 


17.10 


86 


54- 06 


123 


91. 1 


160 


128.4 


197 


165.7 


50 


18.10 


87 


55-05 


124 


92. 1 


161 


129.4 


198 


166.7 


51 


19. 11 


88 


56.05 


125 


93-i 


162 


130.4 


199 


167.7 


52 


20.11 


89 


57.04 


126 


94-1 


163 


I3I-4 


200 


168.7 


53 


21. 11 


90 


58.04 


127 


95-1 


164 


132.4 


201 


169.7 


54 


22.11 


91 


59.03 


128 


96.1 


165 


133-4 


202 


170.7 


55 


23.11 


92 


60.03 


129 


97-1 


166 


134-4 


203 


171. 7 


56 


24.1 1 


93 


61 03 


130 


98.1 


167 


135-4 


204 


172.7 


57 


25.12 


94 


62.02 


131 


99.1 


168 


136.4 


205 


173-7 


58 


26.12 


95 


63.02 


132 


100.2 


169 


137.4 


206 


174.7 


59 


27.12 


96 


64.01 


133 


101.2 


170 


138.5 


207 


175.8 


60 


28.12 


97 


65.01 


134 


102.2 


171 


139-5 


208 


176.8 


61 


29.12 


98 


66.01 


135 


103.2 


172 


140.5 


209 


177.3 


62 


30.12 


99 


67.01 


136 


104.2 


173 


141. 5 


210 


178.8 


63 


31.12 


100 


68.01 


137 


105.2 


174 


142.5 


211 


179.8 


64 


32.12 


101 


69.01 


138 


106.2 


175 


143-5 


212 


180.8 


65 


33-12 


102 


70.00 


139 


107.2 


176 


M4-5 






66 


34- 12 


103 


71.00 


140 


108.2 


177 


145-5 






67 


35.12 


104 


72.0 


141 


109.2 


178 


146.5 






68 


36.12 


105 


73-o 


142 


110.2 


179 


147.5 







VOLUME AND WEIGHT OF DISTILLED WATER. 



Temp. 


Weight of a 


Temp. 


Weight of a 


Temp. 


Weight of a 


Degrees 


Cubic Foot 


Degrees 


Cubic Foot 


Degrees 


Cubic Foot 


Fahr. 


in Pounds. 


Fahr. 


in Pounds. 


Fahr. 


in Pounds. 


32 


62.417 


90 


62.119 


160 


61.007 


39-1 


62.425 


IOO 


62 OOO 


170 


60.801 


40 


62.423 


IIO 


61.867 


ISO 


60.587 


50 


62.409 


120 


61.720 


190 


60.366 


60 


62.367 


I30 


61556 


200 


60.136 


70 


62.302 


I40 


61388 


2IO 


59.894 


80 


62.218 


I50 


61.204 


212 


59.707 



APPENDIX. 



367 



PROPERTIES OF SATURATED STEAM. 
English Units. 



Presure, 


Temperature, 


Heat 


Total 
Heat. 


Heat of 


Volume in 


Weight in 


Pressure, 


Pounds 


Degrees 


of the 


Vaporiza- 


Cu. Ft. of 


Pounds of 1 


Pounds 


per Sq.In. 


Fahr. 


Liquid. 


tion. 


1 Pound. 


Cubic Foot 


per Sq. In. 


P 


t 


S 


A 


r 


s 


d 


/ 


5 


162.34 


I30.7 


II3I-5 


IOOO.8 


73-22 


O.O1366 


5 


10 


193.25 


161. 9 


II4O.9 


979 O 


3S.16 


O.02621 


10 


15 


213.03 


181. 8 


II46.9 


965.I 


26.15 


O.03826 


15 


20 


227.95 


196.9 


II5I.5 


954-6 


19.91 


O.05023 


20 


25 


240.04 


209.1 


II55-1 


946.0 


16.13 


O.06199 


25 


30 


250.27 


219.4 


H5S.3 


938.9 


13-59 


O.07360 


30 


35 


259 19 


228.4 


JI61.O 


932.6 


H-75 


O.08508 


35 


40 


267.13 


236.4 


II63.4 


927.0 


10.37 


O.09644 


40 


45 


274.29 


243.6 


1 165.6 


922.0 


9.287 


O.IO77 


45 


50 


280.85 


250.2 


1167.6 


917.4 


8.414 


O.II88 


50 


55 


2S6.89 


256.3 


H69.4 


913. 1 


7.696 


O.1299 


55 


• 60 


292.51 


261.9 


I 171. 2 


909- 3 


7.096 


O. 1409 


60 


65 


297-77 


267.2 


II72.7 


905-5 


65S3 


O.1519 


65 


70 


302.71 


272.2 


1 1 74- 3 


902. 1 


6-144 


O.1628 


70 


75 


30708 


276.9 


II75-7 


898.8 


5-762 


O.1736 


75 


80 


311. So 


281.4 


1177.0 


895.6 


5 425 


O.1843 


80 


85 


316.02 


2S5.8 


117S.3 


892.5 


5-125 


O.I95I 


85 


90 


320.04 


290.0 


1179.6 


889.6 


4.858 


O.2058 


90 


95 


32389 


294.0 


1180.7 


886.7 


4.619 


O.2165 


95 


100 


327-58 


297.9 


1181.9 


884.0 


4 403 


O.2271 


100 


105 


33 r -i3 


301.6 


1182.9 


8S1.3 


4.206 


O.2378 


105 


110 


334-56 


3052 


1184.0 


878.S 


4.026 


O.2484 


110 


115 


337.86 


30S.7 


11S5.0 


876.3 


3.862 


O.2589 


115 


120 


341-05 


312.0 


1186.0 


S74.0 


3-7H 


0.2695 


120 


125 


344-13 


315.2 


1186.9 


871.7 


3-572 


O.2S0O 


125 


130 


347-12 


318.4 


1187.8 


S69.4 


3-444 


O.2904 


130 


135 


350.03 


321.4 


1188.7 


867.3 


3-323 


O.3009 


135 


140 


352.85 


324.4 


1189-5 


865.1 


3.212 


O.31 13 


140 


145 


355-59 


327.2 


1 190. 4 


863.2 


3.107 


O.3218 


145 


150 


358.26 


330 


1191.2 


861.2 


3. on 


O.3321 


150 


155 


360.86 


332.7 


1192.0 


859.3 


2.919 


O.3426 


155 


160 


363-40 


335-4 


1192.8 


857.4 


2.833 


0.3530 


160 


165 


365.88 


338.o 


II93-6 


855.6 


2.751 


0.3635 


165 


170 


368.29 


340. 5 


II94.3 


853-8 


2 676 


0.3737 


170 


175 


370.65 


343-0 


1195.0 


852.0 


2.603 


O.3841 


175 


180 


372.97 


345 4 


II95.7 


850.3 


2-535 


3945 


180 


185 


375-23 


347-8 


1 196.4 


848.6 


2.470 


O.4049 


185 


190 


377-44 


350.I 


1 197. 1 


847.0 


2.408 


0-4I53 


190 


195 


379-61 


352.4 


1197.7 


845-3 


2-349 


0.4257 


195 


200 


381.73 


354-6 


1198.4 


843.8 


2.294 


0.4359 


200 


205 


383-82 


356.8 


1199.0 


842.2 


2.241 


O.4461 


205 


210 


385.87 


358.9 


1199.6 


840.7 


2.190 


O.4565 


210 


215 


387.8S 


361.0 


1200.2 


839.2 


2.142 


O.4669 


215 


220 


389.84 


363-0 


1200.8 


837.8 


2.096 


0.4772 


220 


225 


391-79 


365-1 


1201.4 


836.3 


2.051 


O.4876 


225 


230 


393.69 


367.1 


1202.0 


834.9 


2.009 


O.4979 


230 


235 


395-56 


369.0 


1202.6 


833.6 


1.968 


O.50S2 


235 


240 


397 4i 


371.0 


1203.2 


832.2 


1.928 


O.51S6 


240 


245 


399.21 


372.8 


1203.7 


830.9 


1. 891 


O 5289 


245 


250 


400. 59 


374 7 


1204.2 


829.5 


1-854 


0-5393 


250 



INDEX 



PAGE 

Accumulators 292, 293 

Acetic acid 71 

Adamson joints 210 

Air for combustion 48, 51 

dilution 51 

loss from excess 61 

per pound of coal 53 

supply for boiler, measurement of 318 

Almy boiler 34 

Angle-valves 237 

Anthracite coal , 37 

Area of circles 362 

steam-pipe 271 

uptake 341 

Areas of segments of circles 360, 361 

Ash-pit 5 

doors 5 

Assembling and riveting boilers. ., 285 

Atmosphere, composition of 49 

Atomic weight , 45 

Babcock & Wilcox 22 

Baird's steam-trap 258 

Belleville boiler 30 

Belpaire fire-box 20, 158. 

Berryman feed-water heater 264 

Blow-off pipes 4, 266 

Blowing out brine 88 

Blue heat 177 

Board of Trade, rules for flues 218 

Boilers, Almy 34 

Babcock & Wilcox 22 

Belleville 30 

369 



37° INDEX. 

PAGE 

Boilers, Cahall 27 

Cornish <, 7 

cylindrical tubular 2 

double-ended 16 

fire-engine 13 

Galloway 7 

gunboat , 18 

Heine.... 25 

Lancashire 6 

Leavitt 20 

locomotive 18, 20 

Manning 9, 10 

marine 14 

(water-tube) 30 

plain cylindrical 6 

Root 25 

Stirling 27 

Thorny croft 32 

two-flue 5 

vertical 9, 11, 12, 13 

water-tube , 21 

(marine) 30 

Yarrow 34 

Boiler accessories 235 

design 523 

explosions 227 

front , 5 

horse-power 135 

Boilers, life of 230 

methods of supporting , 166 

proportions of 138 

Boiler-setting 91 

shop, plan and description of 273 

testing (evaporative) 300 

tubes, size and surface 364 

Boilers, U. S. S. Brooklyn , 146 

Boring-mill 279 

Brackets 166, 353 

Brass 180 

Bridge-wall 2 

Bronze 180 

Buck-staves < 94 

Bumped-up head 186 

Bundy steam-trap 260 

Butt-joint 199, 201 



INDEX. 371 

PAGE 

Cahall boiler 27 

Calculation of riveted joints 192 

stay-rods 347,351 

Calking 298 

Calorimeters for steam, Carpenter 312 

Peabody 309 

Cam and toggle riveting- machine 288 

Carbon, heat of combustion of 43, 44 

Carbonate of lime 68 

Cast iron 1 79 

Chapman valves ... 238 

Channel-bars, calculation of 348, 352 

Charcoal 39 

Check-valves 239 

Chemistry of combustion .... 44 

Chimney draught = 112 

forms of 125 

height of 125 

stability of , 127 

Chimneys 112 

Kent's table 122, 124 

Circles, area of 362 

circumference of 362 

Circumference of circles „ . , 362 

Cleaning fires no 

Coals, anthracite 37 

bituminous 38 

caking, bituminous 38 

dry bituminous 38 

long-flaming bituminous 38 

semi-bituminous 38 

Coal, air per pound of 53 

value of 131 

Cold-water test 299 

Collapsing pressure 207, 210-216 

Coke 38 

Combination 249 

Combustion, air required for 48, 51 

chemistry of 44 

heat of 42-44 

incomplete 60 

rate of 1 36 

temperature of 63 

Composition 180 

of atmosphere 49 



2,7 2 INDEX. 

PAGE 

Composition of fuels 40 

Compression. 175 

Conical through-tubes , 7 

Copper 179 

Cornish boiler 7 

Corrosion 84 

Corrugated furnace , 211 

Crane-lifts 277 

Crown-bars. ... 20, 157 

Crowfeet 152 

Crushing of rivets 191 

Curtis steam-trap 260 

Cylinder, strength of 183, 184 

Cylindrical tubular-boiler setting 91 

staying of 148 

Damper regulator 255 

Density of gases 45 

Detachable brackets 167 

Diameter of boiler 327 

of rivet 192 

Diagonal stays 182 

Du Long's formula 47 

Double-ended boiler 16 

Down-draught furnaces 105 

Draught of chimneys 112 

gauge 316 

Howdens system no 

split 9 

wheel 8 

Drill for tube-holes 278 

Drilled or punched plates 190 

Dry pipe 164 

Dudgeon tube-expander. . < 297 

Economizer, Green's in 

Efficiency of riveted joints • 188 

Elastic limit 174 

Elasticity, modulus of 174 

Equivalent evaporation 133 

Evaporative test of boiler 300 

Excess of air, loss from 61 

Expanders for tubes 296, 297 

Expansion pads 20 

Explosions of boilers 227 



index. 373 

PAGE 

Factor of safety 224, 329 

Farnley furnace 212 

Feed-pipes 4, 264 

pumps 265 

water filter 77 

Feed-water heaters (lime-extracting) 72 

Berryman 264 

Hoppes , 72 

Wainwright 263 

impurities in (table) 66 

organic impurities 81 

Filter, feed-water 77 

Finishing flanges 279 

Fire-doors 5 

engine boiler , , 13 

tubes 2, 220 

Firing 100 

Flange-punch 277 

Flanging heads 275 

Flat plates 222 

Flexible tube 252 

Flow of steam 314 

Flue-gases 316 

Flues 206 

collapsing, pressure of 207, 210-216 

discussion of tests 217 

rules for 218 

strengthened 2o3 

Flynn steam-trap 259 

Forms of test-pieces 171 

Foundation-ring 9 

Fox's corrugated furnace 211 

Friction of riveted joints 191 

Fuel, artificial 39 

standard , , 130 

Fuels, composition of 40, 41, 42 

Furnace, corrugated s . . . 211-216 

Farnley 's 212 

Holmes 213 

Morison's 216 

Purve's 214,215 

Furnaces. . . 95 

down-draught 105 

oil-burning 10S 

Fusible plugs 253 



374 INDEX. 

PAGE 

Gas apparatus, Orsat's. 54 

natural .... 39 

Galloway boiler 7 

General proportions of horizontal multitubular boiler 324 

Girders , , 220 

Globe valves. 235 

Grate-area 325 

bars gS 

water 107 

Grates, rocking gg 

Green's economizer in 

Grooving 87 

Gun boat boile* 18 

Gun iron I7g 

Gusset stays 162, 183 

Hand-holes 4, 166, 342 

Hand-riveting 2g5 

Hangers for pipe 270 

Heat of combustion ... 44 

(carbon) 43, 44 

calculation of 46 

(fuels) 42 

the liquid (water). 366 

Heating-surface. 5, 136, 328 

of boiler-tubes (table) 364 

value of 137 

Heine boiler 25 

Holmes' furnace 213 

Hollow cylinder 183 

Hoppe's purifier. 72 

Horse-power of boilers 135 

Howden's system no 

Hydraulic accumulators 2g2, 2g3 

riveting-machine 288 

with cam and toggle 2g3 

test . . 224, 227 

of boiler 2gg 

Incomplete combustion, loss from 60 

Iron rods, weight of > 363 

Kent's table of chimneys 122 

Kerosene oil . 84 



index. 375 

PAGE 

Lancashire 6 

La P J ( )i, 337 

joints 192, 194 

Lap-joint with welt 196, [98 

Laying out plates 279 

stays 345 

Leavitt boiler 20 

Length of sections 341 

Lever safety-valve 242 

Lewes (marine-boiler scale) 74 

Life of boilers 230 

Lifting-dogs 276 

Lignite 33 

Lime-extracting feed- water heater 72 

Limit of elasticity 174 

Lloyd's rules for flues 21S 

Locke damper regulator. . . „ 256 

Locomotive-boiler iS 

staying of 155 

type 20 

Logarithms 358 

Longitudinal joint 331 

Mahler's composition of fuels 41 

formula 4S 

Malleable iron 179 

Manholes 4, 165, 342 

Manning boilers , 9, 10 

Marine boilers 14 

water-tube , 30 

proportions of 140 

scale 74, 79 

staying of 160 

Materials 1 70 

McDaniels trap 257 

Mechanical stokers 102 

Methods of failure of riveted joints 1S9 

of making boiler-tests 300 

of testing plate 172 

Mineral impurities 67 

matter in water (table) 66 

oil 39 

Modulus of elasticity 174 

Morison's furnace 216 



376 INDEX. 

PAGE 

Natural sines, cos, and tan 362 

trigonometric functions 362 

Naval boilers, proportions of. 141, 142 

Nozzles 342 

Oil-burning furnaces 108 

Organic impurities in feed-water 81 

Orsat's gas apparatus 54 

Peat 38 

Peclet's chimney theory. . . 116 

Peet valve 238 

Petroleums, composition of 40 

Pipe, arrangement of steam 267 

area and size of (Appendix) 

blow-off 266 

feed 265 

hangers for 270 

size for given horse-power 271 

sketches for ordering 269 

Piping 267 

Pitch of rivets 192 

Pitting 85 

Plain cylindrical boiler 6 

Plan of boiler-shop 274 

Planing-machine , 282 

plates 282 

Plate planer , 282 

rolls , 282 

Pop safety-valve 246 

Portable riveting-machine 289 

Power-pump for riveter 290 

Priming 131, 308 

Proportions of boilers 138 

Properties of saturated steam 367 

of steel 176 

Prosser tube-expander 296 

Pumps 265 

Pump for hydraulic riveter 290 

Punch > 282 

and holder 278 

for tube-holes 27S 

Punched or drilled plates 190 

Purve's furnace 214, 215 

Pyrometers 317 



INDEX. Z/7 

PAGE 

Rate of combustion « 136 

Reach of a riveting-machine 289 

Reducing-valve 254 

Reduction of area . . . 175 

Return steam-traps 260 

Ring-seam 336 

Rivet, diameter of 192 

Riveted joints, calculation of 192 

designing 202 

efficiency of 188 

friction of 191 

limitations 205 

methods of failure , 189 

Riveting-machines, cam and toggle 288 

hydraulic 288 

with cam and toggle 293 

portable 289 

steam 294 

Rivets 178 

pitch of , 192 

shearing and crushing 191 

Rocking-grates 99 

Rolls for plate 282 

Roney stoker 103 

Root boiler , 25 

Safety plugs 253 

valve 240 

Sample boiler-test blank 319 

Scale, marine-boiler 74, 79 

Scarfing c 282 

Screw-threads (table) 364 

Sea-water, composition of 74 

Segments of circles 360, 361 

Selection of type of boiler 323 

Semi-bituminous coal 3S 

Separator 262 

Shearing , 175 

of rivets 191 

plates 2S1 

Shears 281 

Shop-practice , 272 

Size and surface of boiler-tubes 364 

of steam-pipe 271 

Sizes of steam, gas, and water pipe (table) 365 



378 INDEX. 

PAGE 

Smoke-box 5 

prevention 104 

Snap-riveting. 295 

Soda 70 

Specific heat 45 

of superheated steam 307 

volumes 45 

Specifications and contract for boiler , . . . 354, 356 

Sphere, strength of 185 

Spherical ends 1 63 

Split-draught 9 

Stability of chimneys 127 

Stay-bolts 156, 181 

Stay-rods 182 

calculation of 347, 351 

Stayed flat plates 222 

Staying , 148 

(calculation of) 343 

cylindrical tubular boiler 148 

laying out 345 

locomotive-boiler 155 

of marine boiler 160 

Stays, diagonal 182 

Steam-dome 163 

flow of 314 

gas, and water pipe (table) 365 

gauges 251 

nozzle 165 

piping 267 

quality of 131 

riveting-machine 294 

space 326 

tables 367 

traps, Baird's 258 

Bundy 260 

Curtis. 260 

Flynn 259 

McDaniel's 257 

return 260 

Walworth 258 

Steel 176 

Stirling boiler 27 

Stokers, mechanical 102 

Strain 174 

Stratton separator 262 



INDEX. 379 

PAGE 

Stress 174 

Stretch limit 174 

Submerged tube-sheet 12 

Sunken tube-sheet 12 

Superheating surface 1 1 

Surface blow 82 

Table of logarithms 353 

Tables of properties of saturated steam 367 

Tannic acid 7 1 

Temperature of combustion 63 

Test on furnace flues 207, 210-216 

Testing boilers for evaporation 300 

Testing-machines , . . 170 

Test-pieces • - 1 7 l 

Testing plate, methods of 172 

Thickness of shell ,. . . 331 

Thornycroft boiler 32 

Throttling calorimeter 309 

Through-stays 2 

Trowbridge's table of chimneys 125 

Tube-expanders 296, 297 

Tube-holes, drills for , 278 

punch for 278 

plates 2 

sheet 339 

Tubes 325 

after expanding 297 

Two flue boiler 5 

Type of boiler, selection of 323 

Ultimate elongation ■ 1 75 

strength 174 

Uptake 2 

area of 341 

U. S. Inspectors' rules for flues 218 

Valves 235 

angle 236 

Chapman 238 

check 239 

gate 23S 

globe 235 

Peet 238 

reducing 254 



380 INDEX. 

PAGE 

Valves safety lever 242 

pop 246 

Vertical boilers 9, 11, 12, 13 

rolls for plate 284 

Volumes, specific , . . . 45 

Wainvvright feed-water heater 263 

Walworth steam-trap 258 

Wash-out plugs 166 

Water column 249 

grate 107 

heat of the liquid 366 

level 328 

tube boilers 21 

boiler-setting 94 

marine boilers. .. . 30 

weight and volume of (table). 366 

Wheel-draught 8 

William's composition of fuels 41 

Wind pressure 127 

Wood 39 

Wrought iron .- 177 

steam, gas, and water pipe 365 

Yarrow boiler 34 

Zinc in boilers , . . , 77 



d 



PLATE I. 




PLATE II. 



-43^— 



-^---lm^ 1 -^ 



i."j 




FIG. 3 




Copper Washer Ck— 1 



FIG. 5 



FIG. 6 



PLATE II. 




FIG. 5 



PLATE III. 




rz% PLUGS E. AND F. 

|E.78^ F. 110%"fROM BACK END. 



B^fevf-f-Mr 



& 



lis 



^,1 \ 3? 

,3? 









'.■2'\V-5 



LONGITUDE 

4 




^ 2}^ PLUG BACK END 

T 

L 

J2}£ PLUG FRONT END 



< REAR ELEVATION 



LOCOMOTIVE BOILER 

160 LBS. PRESSURE 



PLATE III. 



T ^P-'-7f ■ — 7iSl'^~" 

w \ Until- -108ft—- 




FRONT HEAD. SECTION AT X.Y. 
210 TUBES-2"OUTSIDE DIAM. 



LONGITUDINAL SEAM ON OUTSIDE OF FIRE BOX 



2K> PLUG BACK END 



2J4 PLUG FRONT END 



SECTION THROUGH FIRE BOX REAR ELEVATION 



PLATE IV. 





SECTION C-C LOOKING BACK 



NG FRONT. 



PLATE IV. 




SECTION C-C LOOKING BACK 



SECTION A-A LOOKING FRONT 



10 3 Mo 

LOOKING FRONT. 



SHORT-TITLE CATALOGUE 

OF THE 

PUBLICATIONS 

OF 

JOHN WILEY & SONS, 

New York. 

London: CHAPMAN & HALL, Limited. 

ARRANGED UNDER SUBJECTS. 



Descriptive circulars sent on application. 

Books marked with an asterisk are sold at net prices only. 

All books are bound in cloth unless otherwise stated. 



AGRICULTURE. 

Cattle Feeding — Dairy Practice — Diseases of Animals — 
Gardening, Etc. 

Armsby's Manual of Cattle Feeding 12mo, $1 75 

Downing's Fruit and Fruit Trees 8vo, 5 00 

Grotenfelt's The Principles of Modern Dairy Practice. (Woll.) 

12mo, 2 00 

Kemp's Landscape Gardening 12mo, 2 50 

Lloyd's Science of Agriculture 8vo, 4 00 

Loudon's Gardening for Ladies. (Downing.) 12mo, 1 50 

Steel's Treatise on the Diseases of the Dog 8vo, 3 50 

" Treatise on the Diseases of the Ox 8vo, 6 00 

Stockbridge's Rocks and Soils 8vo, 2 50 

Woll's Handbook for Farmers and Dairymen , . . . .12mo, 1 50 

ARCHITECTURE. 

Building — Carpentry— Stairs— Ventilation, Etc 

Berg's Buildings and Structures of American Railroads 4to, 7 50 1 

Birkmire's American Theatres — Planning and Construction. 8vo, 3 00 

" Architectural Iron and Steel 8vo, 3 50 

Birkmire's Compound Riveted Girders 8vo, 2 00 

" Skeleton Construction in Buildings 8vo, 3 00 

1 



Carpenter's Heating and Ventilating of Buildings 8vo, $3 00 

Downing, Cottages 8vo, 2 50 

and Wigktwick's Hints to Architects ,8vo, 2 00 

Preitag's Architectural Engineering 8vo, 2 50 

Gerhard's Sanitary House Inspection 16mo, 1 00 

" Theatre Fires and Panics , 12mo, 1 50 

Hatfield's American House Carpenter 8vo, 5 00 

Holly's Carpenter and Joiner 18mo, 75 

Kidder's Architect and Builder's Pocket-book Morocco flap, 4 00 

Merrill's Stones for Building and Decoration 8vo, 5 00 

Monckton's Stair Building— Wood, Iron, and Stone 4to, 4 00 

Stevens' House Painting 18mo, 75 

Worcester's Small Hospitals — Establishment and Maintenance, 
including Atkinson's Suggestions for Hospital Archi- 
tecture 12mo, 1 25 

World's Columbian Exposition of 1893 4to, 2 50 

ARMY, NAVY, Etc. 

Military Engineering— Ordnance — Port Charges, Etc. 

Bourne's Screw Propellers 4to, 5 00 

Bruff's Ordnance and Gunnery 8vo, 6 00 

Buckuill's Submarine Mines and Torpedoes 8vo, 4 00 

Chase's Screw Propellers 8vo, 3 00 

Cooke's Naval Ordnance 8vo, 12 50 

Cronkhite's Gunnery for Non-com. Officers 18mo, morocco, 2 00 

De Brack's Cavalry Outpost Duties. (Carr.). . . .18mo, morocco, 2 00 

Dietz's Soldier's First Aid 12mo, morocco, 1 25 

* Dredge's Modern French Artillery 4to, half morocco, 20 00 

" Record of the Transportation Exhibits Building, 

World's Columbian Exposition of 1893.. 4to, half morocco, 15 00 

Dyer's Light Artillery 12mo, 3 00 

Hoff's Naval Tactics 8vo, 1 50 

Hunter's Port Charges 8vo, half morocco, 13 00 

Ingalls's Ballistic Tables 8vo, 1 50 

" Handbook of Problems in Direct Fire 8vo, 4 00 

Mahau's Advanced Guard 18mo, 1 50 

Permanent Fortifications. (Mercur.).8vo, half morocco, 7 50 
2 



Mercur's Attack of Fortified Places 12mo, $2 00 

Elements of the Art of War 8vo, 4 00 

Metcalfe's Ordnance and Gunnery 12mo, with Atlas, 5 00 

Phelps's Practical Marine Surveying 8vo, 2 50 

Powell's Army Officer's Examiner 12mo, 4 00 

Reed's Signal Service 50 

SharpeV Subsisting Armies 18mo, morocco, 1 50 

Strauss and Alger's Naval Ordnance and Gunnery 

Todd and Whall's Practical Seamanship 8v6, 7 50 

Very's Navies of the World 8vo, half morocco, 3 50 

Wheeler's Siege Operations 8vo, 2 00 

Winthrop's Abridgment of Military Law 12mo, 2 50 

Woodhull's Notes on Military Hygiene 12mo, morocco, 2 50 

Young's Simple Elements of Navigation.. 12mo, morocco flaps, 2 50 

ASSAYING. 

Smelting — Ore Dressing— Alloys, Etc. 

Fletcher's Quant. Assaying with the Blowpipe.. 12mo, morocco, 1 50 

Furman's Practical Assaying 8vo, 3 00 

Kunhardt's Ore Dressing 8vo, 1 50 

* Mitchell's Practical Assaying. (Crookes.) 8vo, 10 00 

O'Driscoll's Treatment of Gold Ores 8vo, 2 CO 

Pvicketts and Miller's Notes on Assaying 8vo, 3 00 

Thurston's Alloys, Brasses, and Brouzes 8vo, 2 50 

Wilson's Cyanide Processes 12rno, 1 50 

ASTRONOMY. 

Practical, Theoretical, and Descriptive. 

Craig's Azimuth, 4to, 3 50 

Doolittle's Practical Astronomy 8vo, 4 00 

Gore's Elements of Geodesy 8vo, 2 50 

Michie and Harlow's Practical Astronomy 8vo, 3 00 

White's Theoretical and Descriptive Astronomy 12mo, 2 00 

BOTANY. 

Gardening for Ladies, Etc. 

Baldwin's Orchids of New England 8vo, $1 50 

Loudon's Gardening for Ladies. (Downing.) 12mo, 1 50 

3 



2 00 


5 00 


3 50 


5 00 


10 00 


5 00 


2 50 


2 50 


1 25 



Thome's Structural Botany 18mo, $3 25 

Westermaier's General Botany. (Schneider.) 8vo, 2 00* 

BRIDGES, ROOFS, Etc. 

Cantilever — Draw — Highway — Suspension. 
(See also Engineering, p. 6.) 
Boiler's Highway Bridges 8vo, 

* " The Thames River Bridge 4to, paper, 

Burr's Stresses in Bridges 8vo, 

Crehore's Mechanics of the Girder 8vo, 

Dredge's Thames Bridges 7 parts, 

Du Bois's Stresses in Framed Structures 4to, 

Foster's Wooden Trestle Bridges 4to, 

Greene's Arches in Wood, etc 8vo, 

•* Bridge Trusses 8vo, 

" Roof Trusses 8vo, 

Howe's Treatise on Arches 8vo, 

Johnson's Modern Framed Structures ... .4to, 10 00 

Merriman & Jacoby's Text-book of Roofs and Bridges. 

Parti., Stresses 8vo, 2 50 

Merriman & Jacoby's Text-book of Roofs and Bridges. 

Part II., Graphic Statics, 8vo. 2 50 

Merriman & Jacoby's Text-book of Roofs and Bridges. 

Part III., Bridge Design Svo, 5 00 

Merriman & Jacoby's Text-book of Roofs and Bridges. 

Part IV., Continuous, Draw, Cantilever, Suspension, and 

Arched Bridges (In preparation). 

* Morison's The Memphis Bridge Oblong 4to, 10 00 

WaddelPs Iron Highway Bridges 8vo, 4 00 

Wood's Construction of Bridges and Roofs 8vo, 2 00 

Wright's Designing of Draw Spans 8vo, 2 50 

CHEMISTRY. 

Qualitative — Quantitative — Organic — Inorganic, Etc. 

Adriance's Laboratory Calculations 12mo, 1 25 

Allen's Tables for Iron Analysis 8vo, 3 00 

Austen's Notes for Chemical Students 12mo, 1 50 

Bolton's Student's Guide in Quantitative Analysis 8vo, 1 50 

4 



Classen's Analysis by Electrolysis. (Ilerrick.) 8vo, $3 00 

Oafts's Qualitative Analysis. (Schaeffer.) 12rno, 1 50 

Drecbsel's Chemical Reactions. (Merrill.) 12ino, 1 25 

Fresenius's Quantitative Chemical Analysis. (Allen.) 8vo, 6 00 

" Qualitative Chemical Analysis. (Johnson.). .. ..8vo, 4 00 

Gill's Gas and Fuel Analysis 12mo, 1 25 

Hammarsten's Physiological Chemistry (Mandel.) 8vo, 4 00 

Ivolbe's Inorganic Chemistry 12mo, 1 50 

Handel's Bio-chemical Laboratory 12mo, 1 50 

Mason's Water Supply 8vo, 5 00 

Miller's Chemical Physics 8vo, 2 00 

Mixter's Elementary Text-book of Chemistry 12mo, 1 50 

Morgan's Principles of Mathematical Chemistry 12mo, 1 50 

" The Theory of Solutions and its Results 12mo, 1 00 

Nichols's Water Supply (Chemical and Sanitary) 8vo, 2 50 

O'Brine's Laboratory Guide to Chemical Analysis 8vo, 2 00 

Perkins's Qualitative Analysis 12mo, 1 00 

Pinner's Organic Chemistry. (Austen.) 12mo, 1 50 

Ricketts and Russell's Notes on Inorganic Chemistry (Non- 
metallic) Oblong 8vo, morocco, 75 

Schimpf's Volumetric Analysis 12mo, 2 50 

Spencer's Sugar Manufacturer's Handbook . 12mo, morocco flaps, 2 00 

Stockbridge's Rocks and Soils 8vo, 2 50 

Troilius's Chemistry of Iron , 8vo, 2 00 

Wiedemann's Chemical Lecture Notes 12mo, 3 00 

" Sugar Analysis 8vo, 2 50 

Wulling's Inorganic Phar. and Med. Chemistry 12mo, 2 00 

DRAWING. 
Elementary — Geometrical— Topographical. 

Hill's Shades and Shadows and Perspective 8vo, 2 00 

MacCord's Descriptive Geometry 8vo, 3 00 

" Kinematics 8vo, 5 00 

" Mechanical Drawing 8vo, 4 00 

Mahan's Industrial Drawing. (Thompson.) 2 vols., 8vo, 3 50 

Reed's Topographical Drawing. (H. A.) 4to, 5 00 

Smith's Topographical Drawing. (Macmillan.) 8vo, 2 50 

Warren's Descriptive Geometry 2 vols., 8vo, 3 50 

5 



Warreu's Drafting Instruments 12mo, 1 25 

" Free-hand Drawing 12mo, $1 00 

" Higher Linear Perspective 8vo, 3 50 

" Linear Perspective. .. 12mo, 100 

" Machine Construction 2 vols., 8vo, 7 50 

" Plane Problems , 12mo, 125 

" Primary Geometry 12mo, 75 

" Problems and Theorems 8vo, 2 50 

" Projection Drawing 12mo, 150 

Shades and Shadows 8vo, 3 00 

" Stereotomy— Stone Cutting 8vo, 2 50 

Whelpley's Letter Engraving ,12mo, 2 00 

ELECTRICITY AND MAGNETISM. 

Illumination— Batteries— Physics. 

Ant hoi;}' and Brackett's Text-book of Physics (Magie). . . .8vo, 4 00 

Barker's Deep-sea Soundings 8vo, 2 00 

Benjamin's Voltaic Cell 8vo, 3 00 

Cosmic Law of Thermal Repulsion 18mo, 75 

Crehorc and Squier's Experiments with a New Polarizing Photo- 

Chrouograpb 8vo, 3 00 

* Dredge's Electric Illuminatious. . . .2 vols., 4to, half morocco, 25 00 

Vol. II 4to, 7 50 

Gilbert's De magnete. (Mottelay.) 8vo, 2 50 

Holman's Precision of Measurements ■ 8vo, 2 00 

Michie's Wave Motion Relating to Sound and Light, 8vo, 4 00 

Morgan's, The Theory of Solutions and its Results 12mo, 

Niaudet's Electric Batteries. (Fishback.) 12mo, 2 50 

Reagan's Steam and Electrical Locomotives 12rao 2 00 

Thurston's Stationary Steam Engines for Electric Lighting Pur- 
poses 12mo, 1 50 

Tillman's Heat 8vo, 1 50 

ENGINEERING. 
Civil — Mechanical— Sanitary, Etc. 
(See also Bridges, p. 4 ; Hydraulics, p. 8 ; Materials of En- 
gineering, p. 9 ; Mechanics and Machinery, p. 11 ; Steam Engines 
and Boilers, p. 14.) 

Baker's Masonry Construction. „.,„...* .8vo, 5 00 

6 



Baker's Surveying Instruments 12mo, 

Black's U. S. Public Works 4to, 

Butts's Engineer's Field-book 12mo, morocco, 

Byrne's Highway Construction 8vo, 

Carpenter's Experimental Engineering 8vo, 

Church's Mechanics of Engineering — Solids and Fluids 8vo, 

" Notes and Examples in Mechanics 8vo, 

CrandaH's Earthwork Tables 8vo, 

Craudall's The Transition Curve 12mo, morocco, 

* Dredge's Penn. Railroad Construction, etc. . . Folio, half mor., 

- Drinker's Tunnelling 4to, half morocco, 

Eissler's Explosives — Nitroglycerine and Dynamite 8vo, 

Gerhard's Sanitary House Inspection lo'nio, 

Godwin's Railroad Engineer'sField-book.l2mo, pocket-bk. form, 

Gore's Elements of Goodesy 8vo, 

Howard's Transition Curve Field-book 12mo, morocco flap, 

Howe's Retaining Walls (New Edition.) 12mo, 

Hudson's Excavation Tables. Vol. II 8vo, 

Hut ton's Mechanical Engineering of Power Plants 8vo, 

Johnson's Materials of Construction 8vo, 

Johuson's Stadia Reduction Diagram. .Sheet 22A X 28i inches, 

" Theory and Practice of Surveying. 8vo, 

Kent's Mechanical Engineer's Pocket-book 12mo, morocco, 

Kiersted's Sewage Disposal 12mo, 

Kirk wood's Lead Pipe for Service Pipe 8vo, 

Mahan's Civil Engineering. (Wood.) 8vo, 

Merriman and Brook's Handbook for Surveyors. . . .12mo, mor., 

Merriman's Geodetic Surveying 8vo, 

" Retaining Walls and Masonry Dams 8vo, 

Mosely's Mechanical Engineering. (Mahau.) 8vo, 

Nagle's Manual for Railroad Engineers .12mo, morocco, 

Pattou's Civil Engineering 8vo, 

" Foundations 8vo, 

Rockwell's Roads and Pavements in France 12mo, 

Ruffuer's Non-tidal Rivers : 8vo, 

Searles's Field Engineering 12mo, morocco flaps, 

Searles's Railroad Spiral 12mo, morocco 

7 



3 00 


$5 00 


2 50 


5 00 


G 00 


G 00 


2 00 


1 50 


1 50 


20 00 


25 00 


4 00 


1 00 


2 50 




1 50 


1 25 


1 00 


5 00 


6 00 


50 


4 00 


5 00 


1 25 


1 50 


5 00 


2 00 


2 00 


2 00 


5 00 


7 50 


5 00 


1 25 


1 25 


3 00 


1 50 



Siebert and Biggin's Modern Stone Cutting and Masonry. . .8vo, 1 50 

Smith's Cable Tramways 4to, $2 50 

• * Wire Manufacture and Uses 4to, 3 00 

Spalding's Roads and Pavements 12mo, 2 00 

" Hydraulic Cement 12mo, 

Thurston's Materials of Construction 8vo, 5 00 

* Trautwine's Civil Engineer's Pocket-book. ..12mo, mor. flaps, 5 00 

* ' ' Cross-section Sheet, 25 

* Excavations and Embankments 8vo, 2 00 

* " Laying Out Curves 12mo, morocco, 2 50 

Warren's Stereotomy— Stone Cutting 8vo, 2 50 

Webb's Engineering Instruments 12mo, morocco, 1 00 

Wegmann's Construction of Masonry Dams 4to, 5 00 

Wellington's Location of Railways. . - 8vo, 5 00 

Wheeler's Civil Engineering • 8vo, 4 00 

Wolff's Windmill as a Prime Mover 8vo, 3 00 

HYDRAULICS. 

Water-wheels— Windmills — Service Pipe — Drainage, Etc. 
(See also Engineering, p. 6. ) 
Bazin's Experiments upon the Contraction of the Liquid Vein 

(Trautwine) 8vo, 2 00 

Bovey's Treatise on Hydraulics. 8vo, 4 00 

Coffin's Graphical Solution of Hydraulic Problems. 12mo, mor., 

Ferrers Treatise on the Winds, Cyclones, and Tornadoes. . .8vo, 4 00 

Ganguillet & Kutter'sFlow of Water. (Hering& Trautwine ).8vo, 4 00 

Hazen's Filtration of Public Water Supply 8vo, 2 00 

Kiersted's Sewage Disposal 12mo, 1 25 

Kirkwood's Lead Pipe for Service Pipe. 8vo, 1 50 

Mason's Water Supply 8vo, 5 00 

Merriman's Treatise on Hydraulics. 8vo, 4 00 

Nichols's Water Supply (Chemical and Sanitary) 8vo, 2 50 

Ruffner's Improvement for Non-tidal Rivers 8vo, 1 25 

Wegmaun's Water Supply of the City of New York 4to, 10 00 

Weisbach's Hydraulics. (Du Bois.) 8vo, 5 00 

Wilson's Irrigation Engineering, ... 8vo. 4 00 

Wolff's Windmill as a Prime Mover 8vo, 3 00 

Wood's Theory of Turbines 8vo, 2 50 

8 



MANUFACTURES. 

Aniline— Boilers— Explosives— Iron— Sioar— Watches — 
Woollens, Etc. 

Allen's Tables for Iron Analysis 8vo, $3 00 

Beaumont's Woollen and Worsted Manufacture 12mo, 1 50 

Bollaud's Encyclopaedia of Founding Terms 12mo, 3 00 

The Iron Founder 12mo, 2 50 

Supplement 12mo, 2 50 

Booth's Clock and Watch Maker's Manual 12mo, 2 00 

Bouvier's Handbook on Oil Painting 12mo, 2 00 

Eissler's Explosives, Nitroglycerine and Dynamite 8vo, 4 00 

Ford's Boiler Making for Boiler Makers 18mo, 1 00 

Metcalfe's Cost of Manufactures 8vo, 5 00 

Metcalf's Steel— A Manual for Steel Users 12mo, 2 00 

Keimann's Aniline Colors. (Crookes.) 8vo, 2 50 

* Reisig's Guide to Piece Dyeing 8vo, 25 00 

Spencer's Sugar Manufacturer's Handbook. . . .12mo, mor. flap, 2 00 

Svedelius's Handbook for Charcoal Burners 12mo, 1 50 

The Lathe and Its Uses 8vo, 6 00 

Thurston's Manual of Steam Boilers 8vo, 5 00 

West's American Foundry Practice 12mo, 2 50 

•' Moulder's Text-book 12mo, 2 50 

Wiechmann's Sugar Analysis 8vo, 2 50 

Woodbury's Fire Protection of Mills 8vo, 2 50 

MATERIALS OF ENGINEERING. 

Stren gth — Elasticity — Resistance, Etc 

{See also Engineering, p. 6.) 

Baker's Masonry Construction 8vo, 

Beardslee and Kent's Strength of Wrought Iron 8vo, 

Bovey's Strength of Materials 8vo, 

Burr's Elasticity and Resistance of Materials 8vo, 

Byrne's Highway Construction 8vo, 

Carpenter's Testing Machines and Methods of Testing Materials 

Church's Mechanic's of Engineering — Solids and Fluids 8vo, 

Du Bois's Stresses in Framed Structures 4to, 

Hatfield's Trausverse Strains 8vo, 

Johnson's Materials of Construction 8vo, 

9 



5 00 


1 50 


7 50 


5 00 


5 00 


6 00 


.0 00 


5 00 


6 00 



Lanza's Applied Mechanics. 8vo, $7 50 

" Strength of Wooden Columns 8vo, paper, 50 

Merrill's Stones for Building and Decoration 8vo, 5 00 

Merriinan's Mechanics of Materials 8vo, 4 00 

Patton's Treatise on Foundations 8vo, 5 00 

Rockwell's Roads and Pavements in France 12mo, 1 25 

Spalding's Roads and Pavements 12mo, 2 00 

Hydraulic Cement 12mo, 

Thurston's Materials of Construction, 8vo, 5 00 

Thurston's Materials of Engineering 3 vols., 8vo, 8 00 

Vol. I., Non-metallic 8vo, 2 00 

Vol. II., Iron and Steel 8vo, 3 50 

Vol. III., Alloys, Brasses, and Bronzes 8vo, 2 50 

"Weyrauch's Strength of Iron and Steel. (Du Bois.) .8vo, 1 50 

Wood's Resistance of Materials 8vo, 2 00 

MATHEMATICS. 
Calculus— Geometry— Trigonometry, Etc. 

Baker's Elliptic Functions ., . .8vo, 1 50 

Ballard's Pyramid Problem 8vo, 1 50 

Barnard's Pyramid Problem 8vo, 1 50 

Bass's Differential Calculus 12mo, 4 00 

Brigg's Plane Analytical Geometiy 12mo, 1 00 

Chapman's Theory of Equations 12mo, 1 50 

Chessin's Elements of the Theory of Functions 

Compton's Logarithmic Computations 12mo, 1 50 

Craig's Linear Differential Equations 8vo, 5 00 

Davis's Introduction to the Logic of Algebra 8vo, 1 50 

Halsted's Elements of Geometry c..8vo, 175 

" Synthetic Geometry 8vo, 150 

Johnson's Curve Tracing 12mo, 1 00 

" Differential Equations— Ordinary and Partial 8vo, 3 50 

" Integral Calculus 12mo, 1 50 

" Least Squares 12mo, 1 50 

Ludlow's Logarithmic and Other Tables. (Bass.) 8vo, 2 00 

" Trigonometry with Tables. (Bass.) 8vo, 3 00 

Mahan's Descriptive Geometry (Stone Cutting) 8vo, 1 50 

Merriman and Woodward's Higher Mathematics 8vo, 5 00 

Merrirnan's Method of Least Squares 8vo, 2 00 

10 



Parker's Quadrature of the Circle 8vo, $2 50 

Rice and Johnson's Differential and Integral Calculus, 

2 vols, in 1, 12mo, 2 50 

Differential Calculus 8vo, 3 50 

" Abridgment of Differential Calculus 8vo, 1 50 

Searles's Elements of Geometry 8vo, 1 50 

Touch's Metrology 8vo, 2 50 

Warren's Descriptive Geometry 2 vols., 8vo, 3 50 

" Drafting Instruments 12mo, 125 

Free-hand Drawing 12mo, 100 

" Higher Linear Perspective 8vo, 3 50 

" Linear Perspective 12mo, 1 00 

Primary Geometry 12mo, 75 

" Plane Problems. .12mo, 1 25 

" Plane Problems 12mo, 125 

' ' Problems and Theorems 8vo, 2 50 

" Projection Drawing 12mo, 1 50 

Wood's Co-ordinate Geometry 8vo, 2 00 

" Trigonometry 12mo, 1 00 

Woolf's Descriptive Geometry Royal 8vo, 3 00 

MECHANICS-MACHINERY. 

Text-books and Practical Works. 
(See also Engineering, p. 6.) 

Baldwin's Steam Heating for Buildings 12mo, 2 50 

Benjamin's Wrinkles and Recipes 12mo, 2 00 

Carpenter's Testing Machines and Methods of Testing 

Materials 8vo, 

Chordal's Letters to Mechanics 1 2mo, 2 00 

Church's Mechanics of Engineering 8vo, G 00 

" Notes and Examples in Mechanics 8vo, 2 00 

Crehore's Mechanics of the Girder 8vo, 5 00 

Cromwell's Belts and Pulleys 12mo, 1 50 

Toothed Gearing 12mo, 1 50 

Comptou's First Lessons in Metal Working 12mo, 1 50 

Dana's Elementary Mechanics 12mo, 1 50 

Dingey's Machinery Pattern Making 12mo, 2 00 

11 



Dredge's Trans. Exhibits Building, World Exposition, 

4to, half morocco,$15 00 

Du Bois's Mechanics. Vol. I., Kinematics 8vo, 3 50 

Vol.11., Statics 8vo, 4 00 

Vol. Ill, Kinetics 8vo, 3 50 

Fitzgerald's Boston Machinist 18mo, 1 00 

Flather's Dynamometers 12mo, 2 00 

Rope Driving 12mo, 2 00 

Hall's Car Lubrication 12mo, 1 00 

Holly's Saw Filing 18mo, 75 

Lanza's Applied Mechanics 8vo. 7 50 

MacCord's Kinematics 8vo, 5 00 

Merriman's Mechanics of Materials , 8vo, 4 00 

Metcalfe's Cost of Manufactures 8vo, 5 00 

Michie's Analytical Mechanics 8vo, 4 00 

Mosely's Mechanical Engineering. (Mahan.) 8vo, 5 00 

Richards's Compressed Air * 12mo, 1 50 

Robinson's Principles of Mechanism 8vo, 3 00 

Smith's Press-working of Metals 8vo, 3 00 

The Lathe and Its Uses 8vo, 6 00. 

Thurston's Friction and Lost Work 8vo, 3 00 

" The Animal as a Machine 12mo, 1 00 

Warren's Machine Construction 2 vols., 8vo, 7 50 

Weisbach's Hydraulics and Hydraulic Motors. (Du Bois.)..8vo, 5 00 
" Mechanics of Engineering. Vol. III., Part L, 

Sec. I. (Klein.) 8vo, 5 00 

Weisbach's Mechanics of Engineering. Vol. III., Part I., 

Sec. II. (Klein.) 8vo, 5 00 

Weisbach's Steam Engines. (Du Bois.) ■ 8vo, 5 00 

Wood's Analytical Mechanics 8vo, -3 00 

" Elementary Mechanics 12mo, 125 

Supplement and Key . ... 125 

METALLURGY. 

Iron— Gold— Silver — Alloys, Ets. 

Allen's Tables for Iron Analysis 8vo, 3 00 

Egleston's Gold and Mercury 8vo, 7 50 

12 



Egleston's Metallurgy of Silver 8vo, $7 50 

* Kerl's Metallurgy— Copper and Iron 8vo, 15 00 

* " Steel, Fuel, etc 8vo, 15 00 

Kunbardt's Ore Dressing in Europe 8vo, 1 50 

Metcalf Steel— A Manual for Steel Users 12mo, 2 00 

O'Driscoll's Treatment of Gold Ores 8vo, 2 00 

Thurston's Iron and Steel 8vo, 3 50 

Alloys 8vo, 2 50 

"Wilson's C} r anide Processes 12mo, 1 50 

MINERALOGY AND MINING. 

Mine Accidents — Ventilation — Ore Dressing, Etc. 

Beard's Ventilation of Mines 12mo, 

Boyd's Resources of South Western Virginia 8vo, 

Map of South Western Virginia Pocket-book form, 

Brush aud Penfield's Determinative Mineralogy 8vo, 

Chester's Catalogue of Minerals 8vo, 

" Dictionary of the Names of Minerals 8vo, 

Dana's American Localities of Minerals 8vo, 

Descriptive Mineralogy. (E. S.) 8vo, half morocco, 

Mineralogy and Petrography. (J. D. ) 12mo, 

Minerals and How to Study Them. (E. S.) 12mo, 

Text-book of Mineralogy. (E. S.) 8vo, 

inker's Tunnelling, Explosives, Compounds, and Rock Drills. 

4to, half morocco, 

Egleston's Catalogue of Minerals and Synonyms 8vo, 

Eissler's Explosives— Nitroglycerine and Dynamite 8vo, 

Goodyear's Coal Mines of the Western Coast 12mo, 

Hussak's Rock- forming Minerals. (Smith.) 8vo, 

Ihlseng's Manual of Mining 8vo, 

Kunbardt's Ore Dressing in Europe , 8vo, 

O'Driscoll's Treatment of Gold Ores 8vo, 

Rosenbusch's Microscopical Physiography of Minerals and 

Rocks. (Iddings.) 8vo, 

Sawyer's Accidents in Mines 8vo, 

Stockbridge's Rocks and Soils 8vo, 

13 



*Dr: 



2 50 


3 00 


2 00 


3 50 


1 25 


3 00 


1 00 


12 50 


2 00 


1 50 


3 50 


25 00 


2 50 


4 00 


2 50 


2 00 


4 00 


1 50 


2 00 


5 00 


7 00 


2 50 



Williams's Lithology 8vo, $3 00 

Wilson's Mine Ventilation 16mo, 1 25 

STEAM AND ELECTRICAL ENGINES, BOILERS, Etc. 

Stationary— Marine— Locomotive — Gas Engines, Etc. 
(See also Engineering, p. 6.) 

Baldwin's Steam Heating for Buildings 12mo, 

Clerk's Gas Engine t 12mo, 

Ford's Boiler Making for Boiler Makers 18mo, 

Hemen way 's Indicator Practice 1 2mo, 

Hoadley's Warm-blast Furuace 8vo, 

Kneass's Practice and Theory of the Injector 8vo, 

MacCord's Slide Yalve 8vo, 

* Maw's Marine Engines Folio, half morocco, 

Meyer's Modern Locomotive Construction 4to, 

Peabody and Miller's Steam Boilers 8vo, 

Peabody's Tables of Saturated Steam 8vo, 

" Thermodynamics of the Steam Engine 8vo, 

" Yalve Gears for the Steam Engine 8vo, 

Pray's Twenty Years with the Indicator Royal 8vo, 

Pupin and Osterberg's Thermodynamics 12mo, 

Reagan's Steam and Electrical Locomotives 12mo, 

Rontgen's Thermodynamics. (Du Bois.) 8vo, 

Sinclair's Locomotive Running 12mo, 

Thurston's Boiler Explosion 12mo, 

Engine and Boiler Trials 8vo, 

" Manual of the Steam Engine. Part L, Structure 

and Theory, 8vo, 7 50 

Manual of the Steam Engine. Part II., Design, 

Construction, and Operation 8vo, 

2 parts, 

" Philosophy of the Steam Engine 12mo, 

" Reflection on the Motive Power of Heat. (Carnot.) 

12mo, 

" Stationary Steam Engines 12mo, 

" Steam-boiler Construction and Operation 8vo, 

14 



2 50 


4 00 


1 00 


2 00 


1 50 


1 50 


18 00 


10 00 


1 00 


5 00 


2 50 


2 50 


1 25 


2 00 


5 00 


2 00 


1 50 


5 00 



7 50 


12 00 


75 


2 00 


1 50 


5 00 



Spangler's Valve Gears 8v« >, $2 51 1 

Trowbridge's Stationary Steam Engines 4to, boards, 2 50 

Weisbach's Steam Engine. (Du Bois.) 8vo, 

Whitham's Constructive Steam Engineering 8vo, 10 00 

Steam-engine Design 8vo, 6 00 

Wilson's Steam Boilers. (Flather.) 12mo, 2 50 

Wood's Thermodynamics, TIeat Motors, etc 8vo, 4 00 

TABLES, WEIGHTS, AND MEASURES. 

fok actuabies, chemists, engineers, mechanics— metric 
Tables, Etc. 

Adrian ee's Laboratory Calculations 12mo, 1 25 

Allen's Tables for Iron Analysis 8vo, 3 00 

Bixby's Graphical Computing Tables Sheet, 25 

Comptou's Logarithms 12mo, 1 50 

Crandall's Railway and Earthwork Tables 8vo, 1 50 

Egleston's Weights and Measures ISmo, 75 

Fisher's Table of Cubic Yards Cardboard, 25 

Hudson's Excavation Tables. Vol. II 8vo, 1 00 

Johnson's Stadia and Earthwork Tables , 8vo, 1 25 

Ludlow's Logarithmic and Other Tables. (Bass.) 12mo, 2 00 

Thurston's Conversion Tables 8vo, 1 00 

Totten's Metrology 8vo, 2 50 

VENTILATION. 

Steam Heating — House Inspection — Mine Ventilation. 

Baldwin's Steam Heating 12mo, 2 50 

Beard's Ventilation of Mines 12mo, 2 50 

Carpenter's Heating and Ventilating of Buildings 8vo, 3 00 

Gerhard's Sanitary House Inspection Square 16mo, 1 00 

Mott's The Air We Breathe, and Ventilation 16mo, 1 00 

Reid's Ventilation of American Dwellings 12mo, 1 50 

Wilson's Mine Ventilation 16mo, 1 25 

HISCELLANEOUS PUBLICATIONS. 

Alcott's Gems, Sentiment, Language Gilt edges, 5 00 

Bailey's The New Tale of a Tub .8vo, 75 

15 



$1 50 


1 50 


1 50 


4 00 


1 00 


1 50 


3 00 


1 50 


2 50 


25 


3 00 



Ballard's Solution of the Pyramid Problem 8vo, 

Barnard's The Metrological System of the Great Pyramid. .8vo, 
Emmon's Geological Guide-book of the Rocky Mountains. .8vo, 

Ferrel's Treatise on the Winds 8vo, 

Mott's The Fallacy of the Present Theory of Sound. .Sq. 16mo, 

Perkins's Cornell University Oblong 4to, 

Rieketts's History of Rensselaer Polytechnic Institute 8vo, 

Rotherham's The New Testament Critical!}' Emphathized. 

12nao, 

Totteu's An Important Question in Metrology 8vo, 

Wkitehouse's Lake Mceris Paper, 

* Wiley's Yosemite, Alaska, and Yellowstone 4to, 



HEBREW AND CHALDEE TEXT=BOOKS. 

For Schools and Theological Seminaries. 

Gesenius's Hebrew and Chaldee Lexicon to Old Testament. 

(Tregelles.) Small 4to, half morocco, 5 00 

Green's Elementary Hebrew Grammar. 12mo, 1 25 

" Grammar of the Hebrew Language (New Edition). 8 vo, 3 00 

" Hebrew Chrestomathy 8vo, 2 00 

Letteris's Hebrew Bible (Massoretic Notes in English). 

8vo, arabesque, 2 25 
Luzzato's Grammar of the Biblical Cbaldaic Language and the 

Talmud Babli Idioms 12mo, 1 50 

MEDICAL. 

Bull's Maternal Management in Health and Disease 12mo, 1 00 

Hammarsten's Physiological Chemistry. (Mandel.) 8vo, 4 00 

Mott's Composition, Digestibility, and Nutritive Value of Food. 

Large mounted chart, 1 25 

Steel's Treatise on the Diseases of the Ox 8vo, 6 00 

Treatise on the Diseases of the Dog 8vo, 3 50 

Worcester's Small Hospitals — Establishment and Maintenance, 
including Atkinson's Suggestions for Hospital Archi- 
tecture 12mo, 1 25 

16 
















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